Original Activity (original + activity)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Construction of L -Lysine Sensor by Layer-by-Layer Adsorption of L -Lysine 6-Dehydrogenase and Ferrocene-Labeled High Molecular Weight Coenzyme Derivative on Gold Electrode

ELECTROANALYSIS, Issue 24 2008
Haitao Zheng
Abstract A ferrocene-labeled high molecular weight coenzyme derivative (PEI-Fc-NAD) and a thermostable NAD-dependent L -lysine 6-dehydrogenase (LysDH) from thermophile Geobacillus stearothermophilus were used to fabricate a reagentless L -lysine sensor. Both LysDH and PEI-Fc-NAD were immobilized on the surface of a gold electrode by consecutive layer-by-layer adsorption (LBL) technique. By the simple LBL method, the reagentless L -lysine sensor, with co-immobilization of the mediator, coenzyme, and enzyme was obtained, which exhibited current response to L -lysine without the addition of native coenzyme to the analysis system. The amperometric response of the sensor was dependent on the applied potential, bilayer number of PEI-Fc-NAD/LysDH, and substrate concentration. A linear current response, proportional to L -lysine concentration in the range of 1,120,mM was observed. The response of the sensor to L -lysine was decreased by 30% from the original activity after one month storage. [source]


Phytase activity in Cryptococcus laurentii ABO 510

FEMS YEAST RESEARCH, Issue 3 2007
Jason Van Staden
Abstract Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62°C and 5.0, respectively. The enzyme was thermostable at 70°C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, d -glucose 6-phosphate, d -fructose 1,6-diphosphate and p -nitrophenyl phosphate (p -NPP), but its preferred substrate was phytic acid (Km of 21 ,M). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg2+, Zn2+, Cd2+ and Ca2+. These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff. [source]


The effect of drying conditions on the development of the hard-to-cook defect in steam-treated cowpeas

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2006
Nicole S. Affrifah
Summary A three-factor,three-level Box,Behnken design was used to evaluate the effect of drying time, temperature and humidity on textural and physicochemical characteristics during storage of steamed cowpeas. The treatment significantly improved cooked texture and prevented hardening during storage under severe conditions (42 °C/80% relative humidity, RH). Before storage, the cooked texture of treated samples was between 535,628 and 602 N for the untreated control, and between 516,649 and 1394 N after storage at 42 °C/80% RH. The peak force of stored cowpeas significantly decreased as the drying temperature increased. Steaming and drying reduced phytase activity to 59,64% of the original activity and decreased phytate content from 0.133% to 0.074,0.105%. Drying time had a significant effect on phytase activity whereas all drying parameters significantly affected phytate concentration and water absorption. The drying conditions applied after steaming significantly influences seed characteristics; therefore, selection of optimum drying conditions may be used to control seed quality, especially texture. [source]


Novel thermostable serine collagenase from Thermoactinomyces sp.

JOURNAL OF BASIC MICROBIOLOGY, Issue 4 2006
21E: purification, some properties
A thermophilic actinomycete strain Thermoactinomyces sp. 21E producing a highly thermostable serine collagenase was isolated from Bulgarian soil. The collagenase, produced extracellular by Thermoactinomyces sp. 21E, was purified to homogeneity by heat treatment, ultrafiltration, saturation with ammonium sulfate and gel filtration chromatography with a 101-fold increase in specific activity and 58% recovery. The collagenase has a relative molecular mass of 50000 by SDS-PAGE. The optimum temperature for the enzyme activity was 60,65 °C in the absence of Ca2+ and 70,75 °C in the presence of Ca2+. About 40% of the original activity remaining after incubation at 85 °C for 30 min in the presence of Ca2+. The optimum pH for the enzyme activity was 9.0,9.5 and the enzyme was stable for 1h at 70 °C in the pH range from 7.5 to 12.5. The collagenase was strongly inhibited by active-site inhibitors of serine protease PMSF and DFP, which indicated that the enzyme is serine protease. The enzyme activity was completely inhibited by Hg2+, Cu2+ and Fe2+. However, Ca2+ strongly activated the collagenase activity. The collagenase from Thermoactinomyces sp. 21E showed high activity toward type I collagen, acid-soluble collagen, gelatin and Pz-PLGPR. However, elastin for collagenase was inert as substrate. The properties of the collagenase from strain 21E suggest that this enzyme is a new collagenolytic protease that differs from the collagenases and serine proteases reported so far. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


AN ESTEROLYTIC ACTIVITY FROM A WILD EDIBLE MUSHROOM, LYCOPERDON PERLATUM

JOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2009
AHMET COLAK
ABSTRACT Lycoperdon perlatum Pers. (Lycoperdaceae, Agaricales, Agaricomycetidae, Agaricomycetes, Basidiomycota, Fungi) was evaluated for its esterolytic potential. Native electrophoresis of the crude extracts showed four bands having Rf values of 0.34, 0.39, 0.52 and 0.59. The esterase showed the highest activity toward a short-chain substrate, p -nitrophenyl acetate. Optimum reaction conditions for L. perlatum crude extract were attained at pH 8.0 and 40C. Esterolytic activity of enzyme extract was stimulated in the presence of Mn2+, Fe2+, Ca2+ and Zn2+ in the reaction mixture. The enzyme activity was stimulated by incubation at pH 6.0 but retained 77% of its original activity at its optimum pH after 24 h. Thermal inactivation was displayed after incubation for 20 min at various temperatures above 30C. At 1 mM final concentration, 2-mercaptoethanol, dithiothreitol, ethylenediamine tetraacetic acid and p -methylphenyl sulfonylfluoride inhibited the esterolytic reaction. These results support that the crude L. perlatum extract possesses an esterolytic activity having properties similar to other esterases. PRACTICAL APPLICATIONS Esterases catalyzing the cleavage and formation of ester bonds are known ,/,-hydrolases (EC 3.1.1.X). Esterases are used for the synthesis of flavor esters for the food industry, modification of triglycerides for fat and oil industry and resolution of racemic mixtures used for the synthesis of fine chemicals for the pharmaceutical industry. Therefore, the search for new enzyme sources is important for the development of new enzymes and applications. [source]


Transesterification for biodiesel production catalyzed by combined lipases: Optimization and kinetics

AICHE JOURNAL, Issue 6 2010
Yun Liu
Abstract Preparation of biodiesel from waste cooking oil catalyzed by combined lipases in tert -butanol medium was investigated. Several crucial parameters affecting biodiesel yield were optimized by response surface methodology, such as dosage of combined lipases of Novozym 435 and Lipozyme TLIM, weight ratio of Novozym 435 to Lipozyme TLIM, amount of tert -butanol, reaction temperature, and molar ratio of oil to methanol. Under the optimized conditions, the highest biodiesel yield was up to 83.5% The proposed model on biodiesel yield had a satisfactory coefficient of R2 (= 94.02%), and was experimentally verified. The combined lipases exhibited high-operational stability. After 30 cycles (300 h) successively, the activity of combined lipases maintained 85% of its original activity. A reaction kinetic model was proposed to describe the system and deduced to be a pseudo-first-order reaction, and the calculated activation energy was 51.71 kJ/mol. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Purification and biochemical characterisation of a novel glutamate decarboxylase from rice bran

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2010
Li Wang
Abstract BACKGROUND: Glutamate decarboxylase (GAD) is a useful enzyme whose main function is to catalyse the irreversible ,-decarboxylation of L -glutamate to produce ,-aminobutyric acid. The cheap and abundant rice-processing by-product rice bran contains a high amount of GAD, the purification and characterisation of which have not yet been reported. In this study, research on rice bran GAD was initiated. RESULTS: Rice bran GAD was purified to homogeneity via a combined purification protocol of ammonium sulfate fractionation, ion exchange chromatography and two gel filtrations, with a purification fold of 128.6 and an activity recovery of 21.3%. The enzyme was active at pH 5.5 and 40 °C and retained 80% of its original activity in the pH range 5,9 and the temperature range 30,50 °C. GAD activity was significantly enhanced in the presence of Ca2+ but strongly inhibited by Ag+, Hg2+, sodium dodecyl sulfate and CH3COOH. Kinetic determination of the apparent Km for L -glutamate and pyridoxal 5,-phosphate gave values of 27.4 mmol L,1 and 1.16 µmol L,1 respectively. CONCLUSION: Considering that rice bran is cheap and commercially available and that rice bran GAD is relatively stable, the development of cost-effective rice bran GAD-related functional foods would seem to be feasible. Copyright © 2010 Society of Chemical Industry [source]


Degradation of nitroaromatic compounds: a model to study evolution of metabolic pathways

MOLECULAR MICROBIOLOGY, Issue 4 2009
Maia Kivisaar
Summary Although many nitroaromatic compounds have been in nature for only a few decades, bacteria have already evolved the ability to metabolize them. Both horizontal transfer of genes and mutagenesis induced under stressful conditions might facilitate evolution of new catabolic pathways. Nitrotoluene degradation pathways are supposedly derived from an ancestral naphthalene degradation pathway. The 2-nitrotoluene degradation genes in Acidovorax sp. strain JS42 are controlled by the transcriptional activator NtdR, which differs from NagR, the activator of the naphthalene degradation operon in Ralstonia sp. strain U2, by only five amino acids. Both regulators respond to salicylate, an intermediate of naphthalene degradation, but NtdR also recognizes a wide range of nitroaromatic compounds. In this issue of Molecular Microbiology, Ju et al. present results of site-directed mutagenesis of NtdR and NagR and show how the nitrotoluene-responsive regulator NtdR can be generated from a NagR-like ancestor by only a few mutations. The reconstructed hypothetical pathway for the evolution of NtdR from NagR demonstrates stepwise broadening of the effector range of the evolving protein without loss of the original activity. These results provide strong evidence for the idea that promiscuity of proteins is an important step in the evolution of new functions. [source]


Mechanism of DNA Damage Photosensitized by Trisbipyrazyl Ruthenium Complex.

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2000
Unusual Role of Cu/Zn Superoxide Dismutase
ABSTRACT Trisbipyrazyl ruthenium(II) (Ru[bpz]32+) was examined as DNA photosensitizer. Damage resulting from the photolysis of synthetic oligonucleotides has been monitored by polyacrylamide gel electrophoresis. Photoadduct formation is found on both single- and double-stranded oligonucleotides. On oligonucleotide duplex, oxidative damage occurs selectively at the 5,G of the 5,GG3, site and to a lesser extent at the 5,G of a GA sequence. These findings suggest the involvement of electron transfer and show that this mechanism is the main DNA damaging process involved in Ru(bpz)32+ photosensitization. In addition, photoadducts and oxidative damage are both highly affected by an increase of salt concentration in the reaction medium, stressing the importance of direct interactions between nucleic acid bases and the excited ruthenium complex for efficient electron transfer. On single-stranded oligonucleotides, all the guanines are oxidized to the same extent. In this case, oxidative damage, which is not affected by an increase of salt in the solution, has been attributed, in part, to singlet oxygen. More importantly, Cu/Zn superoxide dismutase (SOD) strongly enhances the yield of all damage, correlated to an increase of both electron transfer and singlet oxygen production. This original activity of SOD is the first example of bioactivation of a polyazaaromatic ruthenium complex. [source]


Specificity inversion of Ochrobactrum anthropi D-aminopeptidase to a D,D-carboxypeptidase with new penicillin binding activity by directed mutagenesis

PROTEIN SCIENCE, Issue 9 2005
Michaël Delmarcelle
Abstract The serine penicillin-recognizing proteins have been extensively studied. They show a wide range of substrate specificities accompanied by multidomain features. Their adaptation capacity has resulted in the emergence of pathogenic bacteria resistant to ,-lactam antibiotics. The most divergent enzymatic activities in this protein family are those of the Ochrobactrum anthropi D-aminopeptidase and of the Streptomyces R61 D,D-carboxypeptidase/transpeptidase. With the help of structural data, we have attempted to identify the factors responsible for this opposite specificity. A loop deletion mutant of the Ochrobactrum anthropi D-aminopeptidase lost its original activity in favor of a new penicillin-binding activity. D-aminopeptidase activity of the deletion mutant can be restored by complementation with another deletion mutant corresponding to the noncatalytic domain of the wild-type enzyme. By a second step site-directed mutagenesis, the specificity of the Ochrobactrum anthropi D-aminopeptidase was inverted to a D,D-carboxypeptidase specificity. These results imply a core enzyme with high diversity potential surrounded by specificity modulators. It is the first example of drastic specificity change in the serine penicillin-recognizing proteins. These results open new perspectives in the conception of new enzymes with nonnatural specificities. The structure/specificity relationship in the serine penicillin-recognizing proteins are discussed. [source]


Production, purification and characterisation of a novel halostable xylanase from Bacillus sp.

ANNALS OF APPLIED BIOLOGY, Issue 2 2010
NTU-0
Bacillus sp. NTU-06 was used to produce xylanase, which is an important industrial enzyme used in the pulp and paper industry. The enzyme was purified by fast protein liquid chromatography (FPLC) and had a molecular mass of 24 kDa. The enzyme was active over a concentration range of 0,20% sodium chloride in culture broth, although its activity was optimal in 5% sodium chloride. A salinity stability test showed that 43% of the enzyme activity was retained after 4 h in 20% sodium chloride. Xylanase activity was maximal at pH 8.0 and 40°C. The enzyme was somewhat thermostable, retaining 20% of the original activity after incubation at 70°C for 4 h. The xylanase had Km and Vmax values of 3.45 mg mL,1 and 387.3 µmol min,1mg,1, respectively. The deduced internal amino acid sequence of Bacillus sp. NTU-06 xylanase resembled the sequence of beta-1,4-endoxylanase, which is a member of glycoside hydrolase family 11. Some of the novel characteristics that make this enzyme potentially effective in xylan biodegradation are discussed. [source]


Purification and Characterization of Thermostable ,-Amylase from a Newly Isolated Thermophilic Bacillus stearothermophilus GRE 1

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005
S.M. Zakir Hossain
A thermophilic bacterium, Bacillus stearothermophilus GRE 1, isolated from an Ethiopian hyperthermal spring produced a thermostable ,-amylase. Enzyme production in shake flask experiments while using optimum nutrient supplements and environmental conditions was 2.35 U/ml. Under optimized conditions in a bioreactor, 5-6 fold higher enzyme activity was obtained than that of a shake flask. Gel filtration chromatography yielded a purification factor of 33.62-fold and a recovery of 46.52%. The optimum temperature for activity was determined to be 60-70d,C and optimum pH was in the range of 5.5-6.0. The enzyme maintained 50% of its original activity after 45 minutes of incubation at 80d,C, and is stable at pH values of 5.0-9.0. Enzyme activity was strongly inhibited by Cu2+, Zn2+ and Fe2+. The enzyme is calcium independent and 94% and 86% relative activities were displayed with low concentrations of Co2+ and Mg2+, respectively. [source]