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Malic Enzyme (malic + enzyme)

Distribution by Scientific Domains

Life Sciences	38%
Chemistry	23%
Medical Sciences	15%

Selected Abstracts

Coimmobilization of malic enzyme and alanine dehydrogenase on organic,inorganic hybrid gel fibers and the production of L -alanine from malic acid using the fibers with coenzyme regeneration

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
Koji Nakane
Abstract Malic enzyme (EC 1.1.1.39) and alanine dehydrogenase (EC 1.4.1.1) were entrap-immobilized on hybrid gel fibers of cellulose acetate (CA) and zirconium (Zr) alkoxide by air-gap wet spinning. The production of L -alanine from malic acid with coenzyme regeneration was examined with the enzymes immobilized on the fibers. The productivity of L -alanine of the immobilized enzymes decreased to approximately one-fifth of that of free enzymes, but the CA,Zr-fiber-immobilized enzymes retained a high level of productivity after repeated use. Reduced form of nicotinamide adenine dinucleotide (NADH) recycling also occurred effectively for the enzymes immobilized on the fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

The mode of action of thiazolidinediones,

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue S2 2002
Hans Hauner
Abstract The thiazolidinediones (TZDs) or ,glitazones' are a new class of oral antidiabetic drugs that improve metabolic control in patients with type 2 diabetes through the improvement of insulin sensitivity. TZDs exert their antidiabetic effects through a mechanism that involves activation of the gamma isoform of the peroxisome proliferator-activated receptor (PPAR,), a nuclear receptor. TZD-induced activation of PPAR, alters the transcription of several genes involved in glucose and lipid metabolism and energy balance, including those that code for lipoprotein lipase, fatty acid transporter protein, adipocyte fatty acid binding protein, fatty acyl-CoA synthase, malic enzyme, glucokinase and the GLUT4 glucose transporter. TZDs reduce insulin resistance in adipose tissue, muscle and the liver. However, PPAR, is predominantly expressed in adipose tissue. It is possible that the effect of TZDs on insulin resistance in muscle and liver is promoted via endocrine signalling from adipocytes. Potential signalling factors include free fatty acids (FFA) (well-known mediators of insulin resistance linked to obesity) or adipocyte-derived tumour necrosis factor-, (TNF-,), which is overexpressed in obesity and insulin resistance. Although there are still many unknowns about the mechanism of action of TZDs in type 2 diabetes, it is clear that these agents have the potential to benefit the full ,insulin resistance syndrome' associated with the disease. Therefore, TZDs may also have potential benefits on the secondary complications of type 2 diabetes, such as cardiovascular disease. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Upregulation of glycolytic enzymes in proteins secreted from human colon cancer cells with 5-fluorouracil resistance

ELECTROPHORESIS, Issue 12 2009
Young-Kyoung Shin
Abstract 5-Fluorouracil (5-FU) is the most commonly used chemotherapeutic agent for colorectal cancer (CRC). However, resistance to this drug is a major obstacle in CRC chemotherapy. Accurate prediction of response to 5-FU would avoid unnecessary chemotherapy and allow the selection of other effective drugs. To identify a candidate predictor of 5-FU resistance, we isolated secreted proteins that were up- or downregulated in a 5-FU-resistant cancer cell line, compared with the parent cell line (SNU-C4), using a stable isotope-coded labeling protocol. For validating the clinical applicability of this method, levels of the identified proteins were determined in the sera of 46 patients treated with 5-FU. In total, 238 proteins with molecular weights ranging from 50 to 75,kDa were identified. Among these, 45 and 35 secreted proteins were up- and downregulated in the 5-FU-resistant cell line, respectively. We observed significant upregulation of glycolytic enzymes, including glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase M2 (PK-M2), transketolase, and NADP(+)-dependent malic enzyme 1. In particular, the level of PK-M2, a key enzyme in the glycolytic pathway, showed an increasing tendency in both sera and tissues from CRC patients displaying no response to 5-FU-based chemotherapy (progressive and stable disease cases), compared with that in complete or partial responders to 5-FU-based chemotherapy; however, it did not reach the statistical significance. In conclusion, increasing pattern of PK-M2 observed with 5-FU resistance induced in vitro and in sera and tissues from CRC patients displaying poor response to 5-FU-based chemotherapy suggest the relevance of dysregulated glycolysis and 5-FU-resistant CRC. [source]

Functional role of fumarate site Glu59 involved in allosteric regulation and subunit,subunit interaction of human mitochondrial NAD(P)+ -dependent malic enzyme

FEBS JOURNAL, Issue 4 2009
Ju-Yi Hsieh
Here we report on the role of Glu59 in the fumarate-mediated allosteric regulation of the human mitochondrial NAD(P)+ -dependent malic enzyme (m-NAD-ME). In the present study, Glu59 was substituted by Asp, Gln or Leu. Our kinetic data strongly indicated that the charge properties of this residue significantly affect the allosteric activation of the enzyme. The E59L enzyme shows nonallosteric kinetics and the E59Q enzyme displays a much higher threshold in enzyme activation with elevated activation constants, KA,Fum and ,KA,Fum. The E59D enzyme, although retaining the allosteric property, is quite different from the wild-type in enzyme activation. The KA,Fum and ,KA,Fum of E59D are also much greater than those of the wild-type, indicating that not only the negative charge of this residue but also the group specificity and side chain interactions are important for fumarate binding. Analytical ultracentrifugation analysis shows that both the wild-type and E59Q enzymes exist as a dimer,tetramer equilibrium. In contrast to the E59Q mutant, the E59D mutant displays predominantly a dimer form, indicating that the quaternary stability in the dimer interface is changed by shortening one carbon side chain of Glu59 to Asp59. The E59L enzyme also shows a dimer,tetramer model similar to that of the wild-type, but it displays more dimers as well as monomers and polymers. Malate cooperativity is not significantly notable in the E59 mutant enzymes, suggesting that the cooperativity might be related to the molecular geometry of the fumarate-binding site. Glu59 can precisely maintain the geometric specificity for the substrate cooperativity. According to the sequence alignment analysis and our experimental data, we suggest that charge effect and geometric specificity are both critical factors in enzyme regulation. Glu59 discriminates human m-NAD-ME from mitochondrial NADP+ -dependent malic enzyme and cytosolic NADP+ -dependent malic enzyme in fumarate activation and malate cooperativity. [source]

Coimmobilization of malic enzyme and alanine dehydrogenase on organic,inorganic hybrid gel fibers and the production of L -alanine from malic acid using the fibers with coenzyme regeneration

Pinealectomy reduces hepatic and muscular glycogen content and attenuates aerobic power adaptability in trained rats

JOURNAL OF PINEAL RESEARCH, Issue 1 2007
Cristina das Neves Borges-Silva
Abstract:, The current study emphasizes the crucial role of the pineal gland on the effects of chronic training in different tissues focusing on carbohydrate metabolism. We investigated the maximal oxygen uptake (aerobic power), muscle and liver glycogen content, and also the enzymes involved in the carbohydrate metabolism of rat adipose tissue. Pinealectomized and sham-operated adult male Wistar rats were distributed into four groups: pinealectomized (PINX) untrained, pinealectomized trained, control untrained and control trained. The maximal oxygen uptake capability was assayed before and after the training protocol by indirect open circuit calorimetry. The rats were killed after 8 wk of training. Blood samples were collected for glucose and insulin determinations. The glycogen content was assayed in the liver and muscle. Maximal activities of epididymal adipose tissue enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase and malic enzyme) as well as adipocyte size were determined. The exercise training in control animals promoted an increase in the aerobic power and in liver glycogen content but caused a reduction in the malic enzyme activity in adipose tissue. However, PINX trained animals, in contrast to trained controls, showed a decrease in the aerobic power and in liver and muscle glycogen content, as well as an increase in the activity of the adipocyte enzymes involved in carbohydrate metabolism. In conclusion, these data show that the pineal gland integrity is necessary for the homeostatic control of energy metabolism among adipose, muscle and hepatic tissues. The pinealectomized animals showed alterations in adaptive responses of the maximal oxygen uptake to training. Therefore, the pineal gland must be considered an influential participant in the complex adaptation to exercise and is involved in the improvement of endurance capacity. [source]

Antilipogenic effect of green tea extract in C57BL/6J- Lepob/ob mice

PHYTOTHERAPY RESEARCH, Issue 4 2009
Hye-Jin Kim
Abstract The objective of this study was to determine the effects of green tea extract (GTE) on lipid metabolism in obese animal models. Male C57BL/6J- Lepob/ob mice were divided into control and GTE (0.05 g/100 g diet) groups, which were fed a high-fat (20 g/100 g diet) diet for 12 weeks. Supplementation of GTE significantly reduced (p < 0.01) perirenal and total white adipose tissue weights compared with the control group. Also, the plasma HDL-cholesterol level was significantly higher in the GTE group than in the control group, therefore the GTE group showed a higher HDL-cholesterol/total-cholesterol ratio (HTR) and lower atherogenic index (AI) level than the control group. A reduction of hepatic triglyceride content and adipose tissue weight in the GTE group was related to the suppression of enzyme activities for fatty acid synthesis (glucose-6-phosphate dehydrogenase and malic enzyme) without affecting fatty acid oxidation enzyme (, -oxidation and carnitine palmitoyl transferase) activities in hepatic and adipose tissue. The current results showed that supplementation of green tea extract is beneficial for antiobesity by the suppression of lipogenesis via regulation of related enzyme activities in hepatic and adipose tissue. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Plant-extract-induced changes in the proteome of the soil-borne pathogenic fungus Thielaviopsis basicola

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2010
Joëlle V. F. Coumans
Abstract Thielaviopsis basicola is a hemibiotroph fungus that causes black root rot disease in diverse plants with significant impact on cotton production in Australia. To elucidate how T. basicola growth and proteome are influenced by interactions with natural sources, this fungus was cultured in the presence of root extracts from non-host (wheat, hairy vetch) and susceptible host (cotton, lupin) plants. We found that T. basicola growth was significantly favored in the presence of host extracts, while hierarchical clustering analysis of 2-DE protein profiles of T. basicola showed plant species had a larger effect on the proteome than host/non-host status. Analysis by LC-MS/MS of unique and differentially expressed spots and identification using cross-species similarity searching and de novo sequencing allowed successful identification of 41 spots. These proteins were principally involved in primary metabolism with smaller numbers implicated in other diverse functions. Identification of several "morpho" proteins suggested morphological differences that were further microscopically investigated. Identification of several highly expressed spots suggested that vitamin B6 is important in the T. basicola response to components present in hairy vetch extract, and finally, three spots, induced in the presence of lupin extract, may correspond to malic enzyme and be involved in lipid accumulation. [source]

Liver gene expression in relation to hepatic steatosis and lipid secretion in two duck species

ANIMAL GENETICS, Issue 1 2010
F. Hérault
Summary The susceptibility to development of hepatic steatosis is known to differ between Muscovy and Pekin ducks. Although some experiments were conducted to decipher these differences, few data have been produced to analyse the role of specific genes in this process. For this purpose, expression levels of genes involved in lipid (ATP citrate lyase, malic enzyme 1, fatty acid synthase, stearoyl-CoA desaturase 1, diacylglycerol O-acyl transferase 2, microsomal triglyceride transfer protein, apolipoprotein A1, apolipoprotein B, sterol regulatory element binding factor 1, hepatocyte nuclear factor 4, choline/ethanolamine phosphotransferase 1, carnitine palmitoyl transferase 1A, peroxisome proliferator-activated receptor alpha and sterol O-acyltransferase) and carbohydrate (activating transcription factor 4 or cAMP-response element binding protein, mitochondrial malate dehydrogenase 2 and carbohydrate responsive element binding protein) metabolism and in other functions were analysed in the liver of Pekin and Muscovy ducks fed ad libitum or overfed. A specific positive effect of feeding was observed on the expression of genes involved mainly in fatty acids and TG synthesis and glycolysis, and negative effect on genes involved in ,-oxidation. Interestingly, a strong species effect was also observed on stearoyl-CoA desaturase 1 and to a lesser extent on diacylglycerol O-acyl transferase 2 expression, leading to large differences in expression levels between Pekin and Muscovy overfed ducks, which could explain the difference in lipid metabolism and steatosis ability observed between the two duck species. These results should shed light on gene expression that might underlie susceptibility to hepatic steatosis in humans. [source]

Activities of glucose phosphorylation, glucose-6-phosphatase and lipogenic enzymes in the liver of perch, Perca fluviatilis, after different dietary treatment

AQUACULTURE RESEARCH, Issue 2001
B Borrebaek
Abstract Glucose phosphorylation was increased and the activity of glucose-6-phosphatase was decreased in the liver of perch Perca fluviatilis after feeding previously fasted fish with a high protein/low carbohydrate diet as well as with a diet containing 23% carbohydrate. Activity of the low affinity hexokinase IV (or D), also called glucokinase (GK), was not observed in the liver of perch on the natural diet, fasted perch or perch after feeding with the high protein/low-carbohydrate diet (< 0.2% CHO). How ever, hepatic GK-activity appeared after feeding with the carbohydrate containing diet. By contrast, the activity of hepatic high affinity hexokinase (HK), which was very low in fasted fish, was strongly increased after feeding with the low-carbohydrate as well as the carbohydrate-containing diet. Apparently, HK rather than GK is the hexokinase isoenzyme that is consistently regulated inversely to glucose-6-phosphatase. Activities of the lipogenic enzymes glucose-6-phosphate dehydrogenase, ATP-citrate lyase and malic enzyme were increased by feeding, particularly with the high protein/low carbohydrate diet. Very high levels of hepatic glycogen were observed after both diets. The results are in accordance with the hypothesis that the hepatic high affinity isoenzyme (HK) has a particular anabolic role. [source]

Active and inactive metabolic pathways in tumor spheroids: Determination by GC,MS

BIOTECHNOLOGY PROGRESS, Issue 3 2010
Michael G. Hunnewell
Abstract Active metabolic pathways in three-dimensional cancer-cell cultures are potential chemotherapeutic targets that would be effective throughout tumors. Chaotic vasculature creates cellular regions in tumors with distinct metabolic behavior that are only present in aggregate cell masses. To quantify cancer cell metabolism, transformed mouse fibroblasts were grown as spheroids and fed isotopically labeled culture medium. Metabolite uptake and production rates were measured as functions of time. Gas chromatography,mass spectrometry was used to quantify the extent of labeling on amino acids present in cytoplasmic extracts. The labeling pattern identified several active and inactive metabolic pathways: Glutaminolysis was found to be active, and malic enzyme and gluconeogenesis were inactive. Transformed cells in spheroids were also found to actively synthesize serine, cysteine, alanine, aspartate, glutamate, and proline; and not synthesize glutamine. The activities of these pathways suggest that cancer cells consume glutamine for biosynthesis and not to provide cellular energy. Determining active metabolic pathways indicates how cells direct carbon flow and may lead to the discovery of novel molecular targets for anticancer therapy. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source]

The Effect of Irradiance on Carboxylating/Decarboxylating Enzymes and Fumarase Activities in Mesembryanthemum crystallinum L. Exposed to Salinity Stress

PLANT BIOLOGY, Issue 1 2001
Z. Miszalski
Abstract: In Mesembryanthemum crystallinum plants, treated for 9 days with 0.4 M NaCl at low light intensities (80 - 90 or 95 - 100 ,E m -2 s -1; , = 400 - 700 nm), no day/night malate level differences (,malate) were detected. At high light (385 - 400 ,E m -2 s -1) strong stimulation of PEPC activity, accompanied by a ,malate of 11.3 mM, demonstrated the presence of CAM metabolism. This indicates that, to evolve day/night differences in malate concentration, high light is required. Salt treatment at low light induces and increases the activity of NAD- and NADP-malic enzymes by as much as 3.7- and 3.9-fold, while at high light these values reach 6.4- and 17.7-fold, respectively. The induction of activity of both malic enzymes and PEPC (phospoenolpyruvate carboxylase) take place before ,malate is detectable. An increase in SOD (superoxide dismutase) was observed in plants cultivated at high light in both control and salt-treated plants. However, in salt-treated plants this effect was more pronounced. Carboxylating and decarboxylating enzymes seem to be induced by a combination of different signals, i.e., salt and light intensity. Plants performing CAM, after the decrease of activity of both the decarboxylating enzymes at the beginning of the light period, showed an increase in these enzymes in darkness when the malate pool reaches higher levels. In CAM plants the activity of fumarase (Krebs cycle) is much lower than that in C3 plants. The role of mitochondria in CAM plants is discussed. [source]