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Lipoxygenase
Kinds of Lipoxygenase Terms modified by Lipoxygenase Selected AbstractsKINETIC BEHAVIOR OF SOYBEAN LIPOXYGENASE: A COMPARATIVE STUDY OF THE FREE ENZYME AND THE ENZYME IMMOBILIZED IN AN ALGINATE SILICA SOL-GEL MATRIX,JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2000AN-FEI HSU Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroperoxide into polyunsaturated fatty acids (PUFA). We recently reported a procedure that immobilizes soybean LOX within an alginate sol-gel matrix. In this study, the kinetic profile of free LOX was compared with that of the sol-gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the temperature range of 25,35C. Enzyme activity, measured in aqueous buffer, for both the free and immobilized LOX preparations had Km values of 2.5 and 1.40 mmoles/L, respectively, and Vmax values of 0.056 and 0.02 ,mol/min, respectively. The relative rates of oxidation of linoleic acid and acylgfycerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid >1-monolinolein > 1,3-dilinolein >trilinolein, and for immobilized LOX was linoleic acid >l, 3-dilinolein >1-monolinolein >trilinolein. In general, LOX immobilized in alginate silica sol-gel matrix retained the physical and chemical characteristics of free LOX. [source] Delimiting morphologically identical varieties of soybean [Glycine max (L.) Merr.] using lipoxygenase activitity levelFEDDES REPERTORIUM, Issue 3-4 2005M. S. Ayodele The occurrence of beany flavour resulting from lipoxygenase activity in soybeans was sufficiently manifested in all the 22 varieties of soybean investigated. There were significant differences in the level of lipoxygenase activity among varieties. A positive correlation was observed between lipoxygenase activity and beany flavour. Lipoxygenase activity level was found reliable in delimiting the varieties. A considerable degree of overlaps and associations were observed among the varietal grouping based on lip- oxygenase activity values. Such overlaps corroborate the reported closeness of plant morphological attributes of the varieties. Lipoxygenase activity was therefore, considered a reliable chemotaxonomic tool that could be useful for taxa delimitation, where there are very similar morphological attributes that may hinder easy delimitation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Abgrenzung von morphologisch identischen Varietäten der Soyabohne [Glycine max (L.) Merr.] mittels aktiver Lipoxygenase Das Auftreten eines bohnenähnlichen Geruchs (soybean flavour) als Ergebnis der Lipoxygenase-Aktivität wurde in allen untersuchten 22 Sojabohnen-Sorten eindeutig nachgewiesen. Im Niveau der Lipoxygenase-Aktivität treten zwischen den einzelnen Sorten manifeste Unterschiede auf. Zwischen der Lipoxygenase-Aktivität und dem bohnenartigen Geruch wurde eine positive Korrelation beobachtet. Die Höhe der Lipoxygenase-Aktivität trennt die Sorten zuverlässig. Ein beträchtlicher Grad an Überschneidungen und von Gemeinsamkeiten wurde zwischen den auf Grund der Lipoxygenase-Aktivitätswerte gebildeten Sortengruppen gefunden. Die Überschneidungen bestätigen die Nähe der morphologischen Merkmale der Sorten. Die Lipoxygenase-Aktivität wird daher als eine verlässliche taxonomische Hilfe für die Trennung der Sippen angesehen, deren große morphologische Nähe eine leichte Trennung erschwert. [source] Proton-Coupled Electron Transfer of Unsaturated Fatty Acids and Mechanistic Insight into LipoxygenaseHELVETICA CHIMICA ACTA, Issue 10 2006Shunichi Fukuzumi Abstract A proton-coupled electron transfer (PCET) process plays an important role in the initial step of lipoxygenases to produce lipid radicals which can be oxygenated by reaction with O2 to yield the hydroperoxides stereoselectively. The EPR spectroscopic detection of free lipid radicals and the oxygenated radicals (peroxyl radicals) together with the analysis of the EPR spectra has revealed the origin of the stereo- and regiochemistry of the reaction between O2 and linoleyl (=,(2Z)-10-carboxy-1-[(1Z)-hept-1-enyl]dec-2-enyl) radical in lipoxygenases. The direct determination of the absolute rates of H-atom-transfer reactions from a series of unsaturated fatty acids to the cumylperoxyl (=,(1-methyl-1-phenylethyl)dioxy) radical by use of time-resolved EPR at low temperatures together with detailed kinetic investigations on both photoinduced and thermal electron-transfer oxidation of unsaturated fatty acids provides the solid energetic basis for the postulated PCET process in lipoxygenases. A strong interaction between linoleic acid (=,(9Z,12Z)-octadeca-9,12-dienoic acid) and the reactive center of the lipoxygenases (FeIIIOH) is suggested to be involved to make a PCET process to occur efficiently, when an inner-sphere electron transfer from linoleic acid to the FeIII state is strongly coupled with the proton transfer to the OH group. [source] KINETIC BEHAVIOR OF SOYBEAN LIPOXYGENASE: A COMPARATIVE STUDY OF THE FREE ENZYME AND THE ENZYME IMMOBILIZED IN AN ALGINATE SILICA SOL-GEL MATRIX,JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2000AN-FEI HSU Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroperoxide into polyunsaturated fatty acids (PUFA). We recently reported a procedure that immobilizes soybean LOX within an alginate sol-gel matrix. In this study, the kinetic profile of free LOX was compared with that of the sol-gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the temperature range of 25,35C. Enzyme activity, measured in aqueous buffer, for both the free and immobilized LOX preparations had Km values of 2.5 and 1.40 mmoles/L, respectively, and Vmax values of 0.056 and 0.02 ,mol/min, respectively. The relative rates of oxidation of linoleic acid and acylgfycerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid >1-monolinolein > 1,3-dilinolein >trilinolein, and for immobilized LOX was linoleic acid >l, 3-dilinolein >1-monolinolein >trilinolein. In general, LOX immobilized in alginate silica sol-gel matrix retained the physical and chemical characteristics of free LOX. [source] A Soybean Cultivar Lacking Lipoxygenase 2 and 3 Has Similar Calcium Bioavailability to a Commercial Variety Despite Higher Calcium Absorption InhibitorsJOURNAL OF FOOD SCIENCE, Issue 3 2008H.S.D. Martino ABSTRACT:, The aim of this study was to evaluate calcium bioavailability of a new soybean variety without 2 lipoxygenases with better taste and flavor than a commercial variety containing all 3 isozymes. Using the femur 45Ca uptake method, calcium absorption from a new Brazilian variety, UFV-116, was compared to a common Brazilian variety, OCEPAR 19. Male Sprague,Dawley growing rats weighing 150 to 170 g (10/group) received test meals of whole fat soy flour prepared from UFV-116 or OCEPAR-19 seeds labeled with 10 ,Ci of 45Ca. Femurs were removed after 48 h for determination of 45Ca uptake. Calcium fractional absorption was equivalent between the 2 varieties. The higher oxalate:calcium molar ratio and the higher content of oxalate and phytate (P < 0.05) found in the UFV-116 variety did not affect calcium absorption. Therefore, the new variety is a comparable source of high bioavailable calcium. [source] Thermal Inactivation Kinetics of Peroxidase and Lipoxygenase from Broccoli, Green Asparagus and CarrotsJOURNAL OF FOOD SCIENCE, Issue 1 2002E.F. Morales-Blancas ABSTRACT: Thewermal inactivation curves for peroxidase (POD) and lipoxygenase (LOX) in broccoli (florets), green asparagus (tip and stem), and carrots (cortex and core) extracts were determined in the range of 70 to 95 °C for 0 to 600 s. The capillary tube method was used to obtain quasi-isothermal conditions. The kinetics of both enzymes showed a biphasic first-order model, while at 70 °C, LOX in asparagus showed a monophasic first-order behavior. LOX activity was not detected for carrots. Kinetic parameters, k and Ea, were determined for heat-labile and heatresistant isoenzyme fractions. Additionally, initial and residual activities for both enzymes within tissue sections showed a different distribution and heat stability. [source] Impact of Supercritical Carbon Dioxide and High Pressure on Lipoxygenase and Peroxidase ActivityJOURNAL OF FOOD SCIENCE, Issue 8 2000W. TEDJO ABSTRACT: The effects of supercritical carbon dioxide (ScCO2) treatment and high hydrostatic pressure treatment on the activities of lipoxygenase (LOX) and peroxidase (POD) were studied. Hydrostatic pressure treatment (240 MPa, 55 °C, 15 min) of LOX and POD in 30% sucrose solutions without buffer led to approximately 80% and approximately 50% residual activity, respectively. Application of ScCO2 (35.2 MPa, 40 °C, 15 min for LOX and 62.1 MPa, 55 °C, 15 min for POD) achieved approximately 35% LOX and approximately 65% POD inactivity in 30 % sucrose solutions. Total inactivation of LOX (10.3 MPa, 50 °C and 15 min) and of POD (62.1 MPa, 55 °C and 15 min) could be achieved through ScCO2 treatment of unbuffered solution. Increasing the concentration of sucrose and buffering (pH range 4 to 9) of enzyme solutions resulted in increased resistance of the enzymes to ScCO2 treatment. [source] Evidence for the involvement of lipoxygenase in the oxidative processes associated with the appearance of green staining alteration in the Gordal oliveJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2003Lourdes Gallardo-Guerrero Abstract Lipoxygenase (LOX) activity and chloroplast pigment content were monitored during fruit growth in Gordal and Manzanilla olive varieties (Olea europaea regalis and Olea europaea pomiformis respectively). At all growth stages, LOX activity was greater in Gordal than in Manzanilla, and in both varieties, enzymatic activity peaks coincided with the maximum presence of oxidised chlorophyll pigments in the fruits. The higher lipid peroxidation potential measured directly in vitro and indirectly in vivo in the Gordal variety and its correspondence with higher contents of oxidised catabolites of chlorophyll suggested a greater tendency and sensitivity of this variety to oxidative processes. This could also explain the high organelle disorganisation levels reached during industrial processing of the fruit, allowing the formation of copper,chlorophyll complexes associated with the green staining alteration that affects Gordal olives. Copyright © 2003 Society of Chemical Industry [source] Influence of postharvest water stress on lipoxygenase and alcohol dehydrogenase activities, and on the composition of some volatile compounds of Gewürztraminer grapes dehydrated under controlled and uncontrolled thermohygrometric conditionsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 3 2007L. CHKAIBAN ABSTRACT Gewürztraminer grapes with a sugar content of around 212 g/L (21.7oBrix) were dried at 17oC, 40% relative humidity and 1.5 m/sec air flow in a 300 L thermo-conditioned tunnel. Control grapes were dried traditionally in a window ventilated room, under uncontrolled environmental conditions varying with outside climate. Tunnel-dried grapes reached the desired sugar concentration (305 g/L, 29.5oBrix) in 17 days, loosing 36% of their weight. Control grapes lost only 22% of their weight and grey mould developed in several bunches at the last sampling. Titratable acidity decreased for tunnel-dried and control grapes from 6.5 g/L to 4 g/L and 5 g/L, respectively. Lipoxygenase (LOX) activity declined in both samples from 120 to 90 U/mg protein dw, with a subsequent significant increase after 20% weight loss in tunnel-treated grapes while the control grapes showed a small peak (150 U/mg protein dw) at 13% weight loss. Six carbon compound evolution showed a loose correlation with LOX activity. Alcohol dehydrogenase specific activity and the concentrations of ethanol and of acetaldehyde plus ethyl acetate showed fluctuating patterns of change, with the evolution of these three variables showing similarity, particularly evident in the tunnel-dried grapes. Carotenoids declined significantly, to increase slightly at the end of the experiment in both samples, with the decline more rapid in the control grapes. Traditional, uncontrolled conditions, did not permit constant dehydration, and provoked a rapid stress to the berries (10% of weight loss). Controlled conditions permitted uniform dehydration, postponed water stress, giving a higher quality product without loss of berries. [source] Mung bean lipoxygenase in the production of a C6-aldehyde.BIOTECHNOLOGY JOURNAL, Issue 11 2007Natural green-note flavor generation via biotransformation Abstract Mung bean was investigated as a novel source of lipoxygenase in the natural production of the green-note aroma compound hexanal. Lipoxygenase extracted from mung bean catalyzed the oxidative reaction of linoleic acid, after which the intermediate hydroperoxide compound was split via green bell pepper hydroperoxide lyase to produce hexanal. In comparison to soybean lipoxygenase, mung bean lipoxygenase was found to be a good substitute as it produced 15.4 mM (76% yield) hexanal while soybean gave 60% yield. The mung bean pH profile comprised a wide peak (optimum pH 6.5) representing lipoxygenase-2 and lipoxygenase-3 isozymes, whereas two narrower peaks representing lipoxygenase-1 and lipoxygenase-2/3 isozymes were observed for soybean (optimum pH 10). Extraction at pH 4.5 was preferred, at which specific lipoxygenase activity was also the highest. [source] Lipoxygenase and cyclo-oxygenase products in the control of regional kidney blood flow in rabbitsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2003Jeremy J Oliver Summary 1.,The aim of the present study was to examine the roles of cyclo-oxygenase (COX)- and lipoxygenase (LOX)-dependent arachidonate signalling cascades in the control of regional kidney blood flow. 2.,In pentobarbitone-anaesthetized rabbits treated with NG -nitro- l -arginine and glyceryl trinitrate to ,clamp' nitric oxide, we determined the effects of ibuprofen (a COX inhibitor) and esculetin (a LOX inhibitor) on resting systemic and renal haemodynamics and responses to renal arterial infusions of vasoconstrictors. 3.,Ibuprofen increased mean arterial pressure (14 ± 5%) and reduced medullary laser Doppler flux (MLDF; 26 ± 6%) when administered with esculetin. A similar pattern of responses was observed when ibuprofen was given alone, although the reduction in MLDF was not statistically significant. Esculetin tended to increase renal blood flow (RBF; 16 ± 7%) and MLDF (28 ± 13%) when given alone, but not when combined with ibuprofen. 4.,After vehicle, renal arterial infusions of noradrenaline, angiotensin II and endothelin-1 reduced RBF and cortical laser Doppler flux (CLDF), but not MLDF. In contrast, renal arterial [Phe2,Ile3,Orn8]-vasopressin reduced MLDF but not RBF or CLDF. Ibuprofen alone did not significantly affect these responses. Esculetin, when given alone, but not when combined with ibuprofen, enhanced noradrenaline-induced renal vasoconstriction. In contrast, esculetin did not significantly affect responses to [Phe2,Ile3,Orn8]-vasopressin, angiotensin II or endothelin-1. 5.,We conclude that COX products contribute to the maintenance of arterial pressure and renal medullary perfusion under ,nitric oxide clamp' conditions, but not to renal haemodynamic responses to the vasoconstrictors we tested. Lipoxygenase products may blunt noradrenaline-induced vasoconstriction, but our observations may, instead, reflect LOX-independent effects of esculetin. [source] Sustained increase in arterial blood pressure and vascular resistance induced by infusion of arachidonic acid in ratsACTA PHYSIOLOGICA, Issue 1 2000Kirkebø The haemodynamic responses to arachidonic acid (AA) have been investigated in seven groups of anaesthetized rats. Sodium arachidonate was infused intravenously for 4 or 20 min, and arterial blood pressure was recorded continuously. Cardiac output and organ blood flow were measured by microspheres. Infusion of arachidonate caused first a fast drop in arterial blood pressure, thereafter it increased steadily for 5,15 min towards a pressure about 25 mmHg above control level. The high pressure was maintained for at least 1 h. Repeated infusions of arachidonate gave similar responses. Inhibition of cyclo-oxygenase by indomethacin prevented the initial pressure drop to arachidonate, but not the sustained increase in pressure. Arterial pressure, total vascular resistance and blood flow in the kidneys, adrenals and spleen were significantly reduced, whereas cardiac output was not changed 4 min after start infusion of arachidonate. However, average blood pressure was significantly increased 22 and 35 min after start infusion (from 103.9 ± 2.9 to 128.1 ± 6.1 and 135.8 ± 4.6 mmHg). Mean vascular resistance increased simultaneously (from 3.5 ± 0.2 to 4.7 ± 0.4 and 5.2 ± 0.4 mmHg 100 mL,1), while cardiac output, stroke volume and heart rate were maintained or slightly reduced. The renal blood flow was significantly lowered (from average 4.9 ± 0.1 to 3.3 ± 0.2 and 4.0 ± 0.2 mL min,1). Indomethacin did not prevent the changes in vascular resistance or organ blood flow recorded after 20,35 min. On the other hand, inhibition of both cyclo-oxygenase, lipoxygenase and the cytochrome P450 pathways by eicosatetrayonic acid (ETYA) normalized all haemodynamic parameters. Likewise, the rise in pressure was prevented by 17-octadecynoic acid (17-ODYA), an inhibitor of the cytochrome P450 enzyme activity. Thus, arachidonate infusion caused a transient decrease, and then a sustained increase in arterial pressure and vascular resistance, and a long-lasting reduction in renal blood flow, possibly owing to release of a cytochrome P450 dependent vasoconstrictor metabolite of AA. [source] Effects of Endotoxin Exposure on Cationic Amino Acid Transporter Function in Ovine Peripheral Blood Mononuclear CellsEXPERIMENTAL PHYSIOLOGY, Issue 2 2003Megan F. Clark Rodent models of sepsis differ from clinical human disease in that humans make substantially less whole-body nitric oxide and have different cellular responses to endotoxin. Sheep, when exposed to endotoxin, behave in a manner more similar to humans. Many studies of rodent peripheral blood mononuclear cells (PBMCs) exposed to endotoxin demonstrate increased cationic amino acid transporter function (particularly through the y+ transporter) to supply arginine substrate to upregulated nitric oxide synthase. Whether this is true in sheep is not known. We have studied cationic amino acid transport in sheep PBMCs stimulated with endotoxin, using labelled lysine. PBMCs stimulated both in vitro and in vivo show an initial reduction in total and y+ lysine transport (after 1-2 h exposure to endotoxin): a previously undescribed effect of endotoxin. In in vitro activated cells, the reduction in y+ transport was prevented by the lipoxygenase inhibitor, nordihydroguaretic acid (NDGA), and the phospholipase inhibitor 4-bromophenacyl bromide (4-BPAB), but not cyclohexamide or a number of other inhibitors of intracellular second-messenger pathways. In contrast after 14 h incubation, the expected increase in total and y+ lysine transport was seen. The increase in y+ transport could be prevented by cyclohexamide, dexamethasone, ibuprofen, the protein kinase C inhibitor sphingosine, NDGA and 4-BPAB. These results suggest that in response to endotoxin exposure there is an initial decrease in y+ activity mediated by a lipoxygenase product, followed by a substantial increase in y+ activity mediated by the products of either cyclo-oxygenase or lipoxygenase. Cyclo-oxygenase and/or lipoxygenase inhibition might be useful in reducing arginine transport, and hence nitric oxide production, in these cells. [source] Thrombin induces expression of cytokine-induced SH2 protein (CIS) in rat brain astrocytes: Involvement of phospholipase A2, cyclooxygenase, and lipoxygenaseGLIA, Issue 2 2004Kyung-ae Ji Abstract Previously we have reported that thrombin induces inflammatory mediators in brain glial cells (Ryu et al. 2000. J Biol Chem 275:29955). In the present study, we found that thrombin induced a negative regulator of a cytokine signaling molecule, cytokine-induced SH2 protein (CIS), in rat brain astrocytes. In response to thrombin, CIS expression was increased at both the mRNA and protein levels. Although STAT5 is known to regulate CIS expression, thrombin did not activate STAT5, and inhibitors of JAK2 (AG490) and JAK3 (WHI-P97 and WHI-P154) had little effect on thrombin-induced CIS expression. In contrast, cytosolic phospholipase A2 (cPLA2), cyclooxygenase (COX), and lipoxygenase (LO) play a role in CIS expression, since inhibitors of cPLA2, cyclooxygenase (COX), and LO significantly reduced CIS expression. Reactive oxygen species (ROS) scavengers (N-acetyl-cysteine [NAC] and trolox) reduced thrombin-induced CIS expression, and inhibitors of COX and LO reduced ROS produced by thrombin. Furthermore, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4), products of COX and LO, respectively, potentiated thrombin-induced CIS expression, indicating that ROS, and PGE2 and LTB4 generated by COX and LO, mediate CIS expression. Since interferon-, (IFN-,)-induced GAS-luciferase activity and tyrosine phosphorylation of STAT1 and STAT3 were lower in CIS-transfected cells compared to control vector-transfected cells, CIS could have anti-inflammatory activity. These data suggest that thrombin-stimulation of ROS and prostaglandin and leukotriene production via the cPLA2, COX and LO pathways results in CIS expression. More importantly, CIS expression may be a negative feedback mechanism that prevents prolonged inflammatory responses. © 2004 Wiley-Liss, Inc. [source] 15-hydroxy-eicosatetraenoic acid arrests growth of colorectal cancer cells via a peroxisome proliferator-activated receptor gamma-dependent pathwayINTERNATIONAL JOURNAL OF CANCER, Issue 5 2003George G. Chen Abstract Peroxisome proliferator-activated receptor gamma (PPAR,) inhibits cell growth via promoting apoptosis. Human colorectal cancer tissues had abundant PPAR, but the incidence of apoptosis was very low, suggesting a defect in the PPAR, pathway. Here, we found that 15-hydroxy-eicosatetraenoic acid (15S-HETE), an endogenous ligand for PPAR,, was significantly decreased in the serum of patients with colorectal cancer. Treatment of colon cancer cells with 15S-HETE inhibited cell proliferation and induced apoptosis, which was preceded by an increase in TGF-,-inducible early gene (TIEG) and a decrease in Bcl-2. The action of 15S-HETE could be blocked when PPAR, was suppressed. Overexpression of Bcl-2 prevented the apoptosis. The levels of TIEG and 15-lipoxygenase (15-LOX), the enzyme responsible for 15S-HETE production, was decreased in colorectal cancer. Therefore, colorectal cancer is associated with decreased 15S-HETE. Treatment of colon cancer cells with 15S-HETE inhibits cell proliferation and induces apoptosis in a PPAR,-dependent pathway involving augmentation of TIEG and reduction of Bcl-2 expression. © 2003 Wiley-Liss, Inc. [source] The Effect of Electric Field on Important Food-processing Enzymes: Comparison of Inactivation Kinetics under Conventional and Ohmic HeatingJOURNAL OF FOOD SCIENCE, Issue 9 2004I. Castro ABSTRACT: This work deals with the determination of the inactivation kinetics of several enzymes, most of them used as time-temperature integrators in the food industry. The tested enzymes were polyphenoloxidase, lipoxygenase, pectinase, alkaline phosphatase, and p-galactosidase, and the inactivation assays were performed under conventional and ohmic heating conditions. The thermal history of the samples (conventional and ohmically processed) was made equal to determine if there was an additional inactivation caused by the presence of an electric field, thus eliminating temperature as a variable. All the enzymes followed 1st-order inactivation kinetics for both conventional and ohmic heating treatments. The presence of an electric field does not cause an enhanced inactivation to alkaline phosphatase, pectinase, and ,- galactosidase. However, lipoxygenase and polyphenoloxidase kinetics were significantly affected by the electric field, reducing the time needed for inactivation. The results of the present work can be used industrially to determine processing effectiveness when ohmic heating technology is applied. [source] Factors Influencing the Occurrence of Methanethiol in Aqueous Slurries of Soy Protein ConcentratesJOURNAL OF FOOD SCIENCE, Issue 5 2003Q. Lei ABSTRACT : Aqueous slurries of 6 commercial soy protein concentrate (SPC) contained from 9.8 to 21.7 ppb methanethiol, which corresponds to odor values (in water) of 49 to 108. Effects of temperature (5.5, 24, and 65°C), pH (4.8,6.6, and 9.0), transition metals (FeCl3, FeCl2, and CuCl2), lipoxygenase, and EDTA on methanethiol levels in SPC slurries were investigated. Higher temperature (65°C), basic pH (9.0), transition metals, lipoxygenase, and EDTA caused significant increases in methanethiol compared with the control. CuCl2 caused greater increases in methanethiol than FeCl3 and FeCl2. In contrast, treatments with lower temperature (5.5°C) or acidic pH (4.8) resulted in lower levels of methanethiol in all commercial SPC samples examined. [source] Thermal Inactivation Kinetics of Peroxidase and Lipoxygenase from Broccoli, Green Asparagus and CarrotsJOURNAL OF FOOD SCIENCE, Issue 1 2002E.F. Morales-Blancas ABSTRACT: Thewermal inactivation curves for peroxidase (POD) and lipoxygenase (LOX) in broccoli (florets), green asparagus (tip and stem), and carrots (cortex and core) extracts were determined in the range of 70 to 95 °C for 0 to 600 s. The capillary tube method was used to obtain quasi-isothermal conditions. The kinetics of both enzymes showed a biphasic first-order model, while at 70 °C, LOX in asparagus showed a monophasic first-order behavior. LOX activity was not detected for carrots. Kinetic parameters, k and Ea, were determined for heat-labile and heatresistant isoenzyme fractions. Additionally, initial and residual activities for both enzymes within tissue sections showed a different distribution and heat stability. [source] Inhibition of Oxidative and Antioxidative Enzymes by Trans-ResveratrolJOURNAL OF FOOD SCIENCE, Issue 2 2001X. Fan ABSTRACT: Trans-resveratrol, a phytoalexin produced by a variety of plants, has been shown to inhibit oxidative enzymes in an animal cell system. Its effect on several oxidative and antioxidative enzymes from plants was investigated using in vitro assays. Trans-resveratrol inhibited superoxide dismutase, lipoxygenase, catalase, peroxidase, polyphenol oxidase, and 1-aminocyclopropane-1-carboxylic acid oxidase with apparent KI's of 10, 90, 100, 255, 305, and 350 ,M, respectively. Trans-resveratrol inhibited lipoxygenase activity more effectively than other lipoxygenase inhibitors, including propyl gallate, ibuprofen, ursolic acid, acetylsalicylic acid, and salicylhydroxamic acid. [source] Impact of Supercritical Carbon Dioxide and High Pressure on Lipoxygenase and Peroxidase ActivityJOURNAL OF FOOD SCIENCE, Issue 8 2000W. TEDJO ABSTRACT: The effects of supercritical carbon dioxide (ScCO2) treatment and high hydrostatic pressure treatment on the activities of lipoxygenase (LOX) and peroxidase (POD) were studied. Hydrostatic pressure treatment (240 MPa, 55 °C, 15 min) of LOX and POD in 30% sucrose solutions without buffer led to approximately 80% and approximately 50% residual activity, respectively. Application of ScCO2 (35.2 MPa, 40 °C, 15 min for LOX and 62.1 MPa, 55 °C, 15 min for POD) achieved approximately 35% LOX and approximately 65% POD inactivity in 30 % sucrose solutions. Total inactivation of LOX (10.3 MPa, 50 °C and 15 min) and of POD (62.1 MPa, 55 °C and 15 min) could be achieved through ScCO2 treatment of unbuffered solution. Increasing the concentration of sucrose and buffering (pH range 4 to 9) of enzyme solutions resulted in increased resistance of the enzymes to ScCO2 treatment. [source] Synthesis and biological evaluation of new benzo[f]furo[2,3- h]-and benzo[f]pyrano[2,3- h]coumarin derivatives. ,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2007Maria Tsoukka Furocoumarins 3,5 and pyranocoumarin 7 were synthesized from the reaction of furonaphthalenediones 2,4 and pyranonaphthalenedione 6 respectively with carbethoxymethylene(triphenyl)phosphorane in refluxing DCM for 3-6 hours or under microwave irradiation in toluene for a few minutes. Compounds 3,5,7 and their precursors were tested as anti-inflammatory/antioxidant agents. They were found to compete significantly high DMSO for OH radicals, to scavenge O2, and to inhibit lipoxygenase to a high extent. [source] Isolation of eriocitrin (eriodictyol 7- O -rutinoside) as an arachidonate lipoxygenase inhibitor from Lumie fruit (Citrus lumia) and its distribution in Citrus speciesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2007Yoichi Nogata Abstract An inhibitory compound acting against rat platelet 12-lipoxygenase was isolated from the peel of Lumie fruit (Citrus lumia) by activity-guided separation. It was identified as eriocitrin (eriodictyol 7- O -rutinoside) by spectroscopic analyses. Eriocitrin inhibited 5-lipoxygenase (IC5029.1 µmol L,1) from rat peritoneal polymorphonuclear leukocytes in addition to 12-lipoxygenase (IC5022.3 µmol L,1). Its aglycone, eriodictyol (5,7,3,, 4,-tetrahydroxyflavanone), was a much more potent inhibitor of both 12-lipoxygenase (IC500.07 µmol L,1) and 5-lipoxygenase (IC500.20 µmol L,1). It also inhibited the production of leukotriene B4 in intact peritoneal polymorphonuclear leukocytes stimulated with calcium ionophore A23187 (IC5012.7 µmol L,1). The distribution of eriocitrin in 39 citrus fruits was investigated by high-performance liquid chromatography analysis. Lumie, eureka lemon (Citrus limon), Sambokan (Citrus sulcata), Sudachi (Citrus sudachi) and Koji (Citrus leiocarpa) fruits were found to contain high levels of eriocitrin in both peel and juice vesicles. Copyright © 2006 Society of Chemical Industry [source] Measurement of lipoxygenase in Australian white wheat flour: the effect of lipoxygenase on the quality properties of white salted noodlesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2006Larisa Cato Abstract The enzyme lipoxygenase has a number of functions in breadmaking. Although white salted noodles are a staple food in various countries, the significance and potential of lipoxygenase in noodlemaking are less well understood. In these products a bright, uniform appearance is particularly important and so the aim of the present research has been to study the effect of endogenous and exogenous lipoxygenase upon discolouration of white salted noodles as well as on the textural and structural attributes. Similar lipoxygenase levels were recorded in the flours studied and no significant losses of activity were found during noodle manufacture and subsequent storage. Less discolouration occurred in treated noodle sheets compared with control samples. Discolouration happened to a lesser extent when samples were cooked immediately after preparation or drying for both treated and control noodles. Whiter noodle sheets were obtained when a soybean lipoxygenase was added to the formulation. Textural and structural properties of white salted noodles were not adversely affected by enzyme addition, giving firm, elastic and non-sticky products. It is concluded that the incorporation of the lipoxygenase preparation offers prospects for colour enhancement of white salted noodles. Copyright © 2006 Society of Chemical Industry [source] Evidence for the involvement of lipoxygenase in the oxidative processes associated with the appearance of green staining alteration in the Gordal oliveJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2003Lourdes Gallardo-Guerrero Abstract Lipoxygenase (LOX) activity and chloroplast pigment content were monitored during fruit growth in Gordal and Manzanilla olive varieties (Olea europaea regalis and Olea europaea pomiformis respectively). At all growth stages, LOX activity was greater in Gordal than in Manzanilla, and in both varieties, enzymatic activity peaks coincided with the maximum presence of oxidised chlorophyll pigments in the fruits. The higher lipid peroxidation potential measured directly in vitro and indirectly in vivo in the Gordal variety and its correspondence with higher contents of oxidised catabolites of chlorophyll suggested a greater tendency and sensitivity of this variety to oxidative processes. This could also explain the high organelle disorganisation levels reached during industrial processing of the fruit, allowing the formation of copper,chlorophyll complexes associated with the green staining alteration that affects Gordal olives. Copyright © 2003 Society of Chemical Industry [source] Lipoxin A4 generation is decreased in aspirin-sensitive patients in lysine-aspirin nasal challenge in vivo modelALLERGY, Issue 12 2009M. Kupczyk Background:, Lipoxins represent a group of lipoxygenase derived eicosanoids which, in contrast to leukotrienes, are potent anti-inflammatory mediators. The aim of our study was to determine lipoxin A4 (LXA4) and leukotriene C4 (LTC4) levels in nasal lavages after intranasal challenge with aspirin in aspirin intolerant (AIA) in comparison to aspirin tolerant (ATA) asthmatics and after allergen challenge in patients suffering from allergic rhinitis. Methods:, Twelve AIA, 8 ATA and 20 allergic patients were challenged with placebo, 16 mg of lysine-aspirin (Lys-ASA) or allergen (grasses). Nasal lavages were collected and eicosanoids' levels were determined using ELISA. Results:, Clinically positive Lys-ASA challenge in AIA resulted in influx of leukocytes (eosinophils and basophils) to nasal secretions and increase of LTC4 to 106.82 pg/ml (P < 0.05 vs baseline (26.58 pg/ml)) on first hour after the challenge. We did not observe any differences in LTC4 level before and after ASA challenge in ATA. In AIA group the mean level of LXA4 was 43 ± 21.5 pg/ml after placebo and decreased in 2 h after Lys-ASA challenge (29 ± 17 pg/ml, P = 0.015). We found an increase in LXA4 in ATA after ASA provocation as compared to placebo (33 ± 16 pg/ml vs 52 ± 31 pg/ml, P = 0.046). In atopic patients baseline level of LXA4 was 33.49 ± 16.95 pg/ml with no difference after the clinically positive allergen challenge (36.22 ± 13.26 pg/ml, P = 0.23). Conclusions:, Results of our study confirm that AIA have diminished LXs' biosynthesis capacities in vivo after ASA challenge. Taking into consideration anti-inflammatory properties of lipoxins this phenomenon may be partially responsible for the development of chronic inflammation in AIA patients. [source] Degradation of normal and proliferated peroxisomes in rat hepatocytes: Regulation of peroxisomes quantity in cellsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2003Sadaki Yokota Abstract Degradation and turnover of peroxisomes is reviewed. First, we describe the historical aspects of peroxisome degradation research and the two major concepts for breakdown of peroxisomes, i.e., autophagy and autolysis. Next, the comprehensive knowledge on autophagy of peroxisomes in mammalian and yeast cells is reviewed. It has been shown that proliferated peroxisomes are degraded by selective autophagy, and studies using yeast cells have been especially helpful in shedding light on the molecular mechanisms of this process. The degradation of extraperoxisomal urate oxidase crystalloid is noted. Overexpressed wild-type urate oxidase in cultured cells has been shown to be degraded through an unknown proteolytic pathway distinct from the lysosomal system including autophagy or the ubiquitin-proteasome system. Finally, peroxisome autolysis mediated by 15-lipoxygenase (15-LOX) is described. 15-LOX is integrated into the peroxisome membrane causing focal membrane disruptions. The content of the peroxisomes is then exposed to cytosol proteases and seems to be digested quickly. In conclusion, the number of peroxisomes appears to be regulated by two selective pathways, autophagy, including macro- and microautophagy, and 15-LOX-mediated autolysis. Microsc. Res. Tech. 61:151,160, 2003. © 2003 Wiley-Liss, Inc. [source] Expression analysis of genes induced in barley after chemical activation reveals distinct disease resistance pathwaysMOLECULAR PLANT PATHOLOGY, Issue 5 2000Katrin Beßer Salicylic acid (SA) and its synthetic mimics 2,6-dichloroisonicotinic acid (DCINA) and benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH), protect barley systemically against powdery mildew (Blumeria graminis f.sp. hordei, Bgh) infection by strengthening plant defence mechanisms that result in effective papillae and host cell death. Here, we describe the differential expression of a number of newly identified barley chemically induced (BCI) genes encoding a lipoxygenase (BCI-1), a thionin (BCI-2), an acid phosphatase (BCI-3), a Ca2+ -binding EF-hand protein (BCI-4), a serine proteinase inhibitor (BCI-7), a fatty acid desaturase (BCI-8) and several further proteins with as yet unknown function. Compared with SA, the chemicals DCINA and BTH were more potent inducers of both gene expression and resistance. Homologues of four BCI genes were detected in wheat and were also differentially regulated upon chemical activation of disease resistance. Except for BCI-4 and BCI-5 (unknown function), the genes were also induced by exogenous application of jasmonates, whereas treatments that raise endogenous jasmonates as well as wounding were less effective. The fact that BCI genes were not expressed during incompatible barley,Bgh interactions governed by gene-for-gene relationships suggests the presence of separate pathways leading to powdery mildew resistance. [source] Time-course of lipoxygenase, antioxidant enzyme activities and H2O2 accumulation during the early stages of Rhizobium,legume symbiosisNEW PHYTOLOGIST, Issue 1 2001Pablo Bueno Summary ,,The involvement of lipoxygenase and antioxidant enzyme activities as well as hydrogen peroxide (H2O2) accumulation are reported during early infection steps in alfalfa (Medicago sativa) roots inoculated either with a wild type Sinorhizobium meliloti or with a mutant defective in Nod-factor synthesis (Nod C,). ,,Compatibility between M. sativa and Rhizobium correlates, at least in part, with an increase in the activities of these enzymes, particularly catalase and lipoxygenase, during the preinfection period (up to 12 h). The mutant strain, defective in Nod-factor biosynthesis, showed a decrease in all enzyme activities assayed, and an increase in H2O2 accumulation. ,,Enhancement of scavenging activities for several reactive oxygen species correlated with compatibility of the S. meliloti,alfalfa symbiosis, whereas the Nod C, strain triggered a defence response. Nod factors were essential to suppress this response. ,,Increase in lipoxygenase and lipid hydroperoxide decomposing activities, observed during the first hours after inoculation with a compatible strain, could be related to tissue differentiation and/or the production of signal molecules involved in autoregulation of nodulation by the plant. [source] PGPR and entomopathogenic fungus bioformulation for the synchronous management of leaffolder pest and sheath blight disease of ricePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2010Loganathan Karthiba Abstract BACKGROUND: The biological control of plant pests and diseases using a single organism has been reported to give inconsistent and poor performance. To improve the efficacy, bioformulations were developed possessing mixtures of bioagents. RESULTS: Bioformulations combining Pseudomonas fluorescens Migula strains Pf1 and AH1 and Beauveria bassiana (Balsamo) Vuill. isolate B2 were developed and tested for their efficacy against leaffolder pest and sheath blight disease on rice under glasshouse and field conditions. The combination of Pf1, AH1 and B2 effectively reduced the incidence of leaffolder insect and sheath blight disease on rice compared with other treatments. An in vitro assay of leaffolder preference to rice leaf tissues treated with Pf1 + AH1 + B2 biformulation showed variation from normal growth and development of leaffolder larvae. Plants treated with the Pf1 + AH1 + B2 combination showed a greater accumulation of enzymes, lipoxygenase and chitinase activity against leaffolder insect compared with other treatments. Similarly, the plants showed a higher accumulation of defence enzymes, peroxidase and polyphenol oxidase activity against sheath blight pathogen in Pf1 + AH1 + B2 treatment compared with the untreated control. The bioformulation mixture attracted the natural enemy population of leaffolder under field conditions. In addition, a significant increase in rice grain yield was observed in Pf1 + AH1 + B2 treatment compared with the untreated control. CONCLUSION: The combination of P. fluorescens strains and B. bassiana isolate effectively reduced the incidence of leaffolder insect and sheath blight disease on rice plants and showed the possibility of controlling both pest and disease using a single bioformulation. Copyright © 2010 Society of Chemical Industry [source] Effects of progressive drought stress on the expression of patatin-like lipid acyl hydrolase genes in Arabidopsis leavesPHYSIOLOGIA PLANTARUM, Issue 1 2008Ana Rita Matos Patatin-like genes have recently been cloned from several plant species and found to be involved in stress responses and development. In previous work, we have shown that a patatin-like gene encoding a galactolipid acyl hydrolase (EC 3.1.1.26) was stimulated by drought in the leaves of the tropical legume, Vigna unguiculata L. Walp. The aim of the present work was to study the expression of patatin-like genes in Arabidopsis thaliana under water deficit. Expression of six genes was studied by reverse transcriptase polymerase chain reaction in leaves of plants submitted to progressive drought stress induced by withholding water and also in different plant organs. Three genes, designated AtPAT IIA, AtPAT IVC and AtPAT IIIA, were shown to be upregulated by water deficit but with different kinetics, while the other patatin-like genes were either constitutive or not expressed in leaves. The accumulation of transcripts of AtPAT IIA in the early stages of the drought treatment was coordinated with the upregulation of lipoxygenase and allene oxide synthase genes. AtPAT IIA expression was also induced by wounding and methyl jasmonate treatments. The in vitro lipolytic activity toward monogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidylcholine and phosphatidylglycerol was confirmed by producing the recombinant protein ATPAT IIA in insect cells. The analysis of free fatty acid pools in drought-stressed leaves shows an increase in the relative amounts of trans-3-hexadecenoic acid at the beginning of the treatment followed by a progressive accumulation of linoleic and linolenic acids. The possible roles of AtPAT IIA in lipid signaling and membrane degradation under water deficit are discussed. [source] | ||||||||||||||||||||||||||||