Purification and characterization of an intracellular beta-glucosidase from the protoplast fusant of Aspergillus oryzae and Aspergillus niger

Protoplasts of Aspergillus oryzae 3.481 and Aspergillus niger 3.316 were prepared using cellulose and snail enzyme with 0.6 M NaCl as osmotic stabilizer. Protoplast fusion has been performed using 35% polyethylene glycol 4.000 with 0.01 mM CaCl2. The fused protoplasts have been regenerated on regeneration medium and fusants were selected for further studies. An intracellular beta-glucosidase (EC 3.2.1.21) was purified from the protoplast fusant of Aspergillus oryzae 3.481 and Aspergillus niger 3.316 and characterized. The enzyme was purified 138.85-fold by ammonium sulphate precipitation, DE-22 ion exchange and Sephadex G-150 gel filtration chromatography with a specific activity of 297.14 U/mg of protein. The molecular mass of the purified enzyme was determined to be about 125 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The enzyme had an optimum pH of 5.4 and temperature of 65 degrees C, respectively. This enzyme showed relatively high stability against pH and temperature and was stable in the pH range of 3.0-6.6. Na+, K+, Ca2+, Mg2+ and EDTA completely inhibited the enzyme activity at a concentration of 10 mM. The enzyme activity was accelerated by Fe3+. The enzyme activity was strongly inhibited by glucose, the end product ofglucoside hydrolysis. The K(m) and V(max) values against salicin as substrate were 0.035 mM and 1.7215 micromol min(-1), respectively.     

Isolation and characterization of NADP+-linked isocitrate dehydrogenase of germinating pea seeds (Pisum sativum)

NADP+-linked isocitrate dehydrogenase (E.C.1.1.1.42) has been purified to homogeneity from germinating pea seeds. The enzyme is a tetrameric protein (mol wt, about 146,000) made up of apparently identical monomers (subunit mol wt, about 36,000). Thermal inactivation of purified enzyme at 45 degrees and 50 degrees C shows simple first order kinetics. The enzyme shows optimum activity at pH range 7.5-8. Effect of substrate [S] on enzyme activity at different pH (6.5-8) suggests that the proton behaves formally as an "uncompetitive inhibitor". A basic group of the enzyme (site) is protonated in this pH range in the presence of substrate only, with a pKa equal to 6.78. On successive dialysis against EDTA and phosphate buffer, pH 7.8 at 0 degrees C, yields an enzymatically inactive protein showing kinetics of thermal inactivation identical to the untreated (native) enzyme. Maximum enzyme activity is observed in presence of Mn2+ and Mg2+ ions (3.75 mM). Addition of Zn2+, Cd2+, Co2+ and Ca2+ ions brings about partial recovery. Other metal ions Fe2+, Cu2+ and Ni2+ are ineffective.     

黑曲霉(Aspergillus niger)β-D-葡萄糖苷酶的纯化及其性质

利用垂直板凝胶制备电泳从黑曲霉(Aspergillus niger,AS 3.316)中分离提纯了β-D-葡萄糖苷酶(EC3.2.1.21),经凝胶电泳鉴定为单一带。酶作用的最适pH为4.4,在pH4.0—6.2稳定;最适温度65℃,热稳定性较好,于60℃保温4小时,活力保留80％。此酶作用于纤维二糖的Km值为6.09mM。聚丙烯酰胺薄层等电聚焦测得其pI值为5.5;用SDS凝胶电泳测得其分子量为77000。此酶不仅能水解纤维二糖和对硝基苯-β-D-葡萄糖苷,还能微弱地水解对硝基苯β-D-半乳糖苷和β-D-木糖苷。金属离子Fe~(2+)、Hg~(2+)、Cu~(2+)、Al~(3+)、Hg~+和Ag~+等对此酶有不同程度的抑制作用,蛋白质侧链修饰剂N-溴代琥珀酰亚胺对此酶有较强的抑制作用,2-羟基-5-硝基溴苯对酶也有一定的抑制作用,推测色氨酸残基对β-D-葡萄糖苷酶的活力是非常必要的。     

Partial purification and characterization of human erythrocyte phosphoglycollate phosphatase.

Human erythrocytes contain a phosphatase that is highly specific for phosphoglycollate. It shows optimum pH of 6.7 and has Km 1 mM for phosphoglycollate. The molecular weight appears to be about 72000. The enzyme is a dimeric molecule having subunits of mol. wt. about 35000. It could be purified approx. 4000-fold up to a specific activity of 5.98 units/mg of protein. The activity of the enzyme is Mg2+-dependent. Co2+, and to a smaller extent Mn2+, may substitute for Mg2+. Half-maximum inhibition of the phosphatase by 5,5'-dithiobis-(2-nitrobenzoate), EDTA and NaF is obtained at 0.5 microM, 1 mM and 4 mM respectively. Moreover, it needs a univalent cation for optimum activity. Phosphoglycollate phosphatase is a cytoplasmic enzyme. Approx. 5% of its total activity is membrane-associated. This part of activity can be approx. 70% solubilized by freezing, thawing and treatment with 0.25% Triton X-100.     

Purification and properties of endo-alpha-1,3-glucanase from a Streptomyces chartreusis strain.

An enzyme hydrolyzing the water-insoluble glucans produced from sucrose by Streptococcus mutans was purified from the culture concentrate of Streptomyces chartreusis strain F2 by ion-exchange chromatography on diethylaminoethyl cellulose and carboxymethyl cellulose columns and gel filtration on Bio-Gel A-1.5m. The purification achieved was 6.4-fold, with an overall yield of 27.3%. Electrophoresis of the purified enzyme protein gave a single band on a sodium dodecyl sulfate-polyacrylamide gel slab. Its molecular weight was estimated to be approximately 68,000, but there is a possibility that the native enzyme exists in an aggregated form or is an oligomer of the peptide subunits, have a molecular weight larger than 300,000. The pH optimum of the enzyme was 5.5 to 6.0, and its temperature optimum was 55 degrees C. The enzyme lost activity on heating at 65 degrees C for 10 min. The enzyme activity was completely inhibited by the presence of 1 mM Mn2+, Hg2+, Cu2+, Ag2+, or Merthiolate. The Km value for the water-insoluble glucan of S. mutans OMZ176 was an amount of glucan equivalent to 1.54 mM glucose, i.e., 0.89 mM in terms of the alpha-1,3-linked glucose residue. The purified enzyme was specific for glucans containing an alpha-1,3-glucosidic linkage as the major bond. The enzyme hydrolyzed the S. mutans water-insoluble glucans endolytically, and the products were oligosaccharides. These results indicate that the enzyme elaborated by S. chartreusis strain F2 is an endo-alpha-1,3-glucanase (EC 3.2.1.59).     

Characterization and molecular cloning of a heterodimeric beta-galactosidase from the probiotic strain Lactobacillus acidophilus R22

Beta-galactosidase from the probiotic strain Lactobacillus acidophilus R22 was purified to apparent homogeneity by ammonium sulphate fractionation, hydrophobic interaction, and affinity chromatography. The enzyme is a heterodimer consisting of two subunits of 35 and 72 kDa, as determined by gel electrophoresis. The optimum temperature of beta-galactosidase activity was 55 degrees C (10-min assay) and the range of pH 6.5-8, respectively, for both o-nitrophenyl-beta-D-galactopyranoside (oNPG) and lactose hydrolysis. The Km and Vmax values for lactose and oNPG were 4.04+/-0.26 mM, 28.8+/-0.2 micromol D-glucose released per min per mg protein, and 0.73+/-0.07 mM, 361+/-12 micromol o-nitrophenol released per min per mg protein, respectively. The enzyme was inhibited by high concentrations of oNPG with Ki,s=31.7+/-3.5 mM. The enzyme showed no specific requirements for metal ions, with the exception of Mg2+, which enhanced both activity and stability. The genes encoding this heterodimeric enzyme, lacL and lacM, were cloned, and compared with other beta-galactosidases from lactobacilli. Beta-galactosidase from L. acidophilus was used for the synthesis of prebiotic galacto-oligosaccharides (GOS) from lactose, with the maximum GOS yield of 38.5% of total sugars at about 75% lactose conversion.     

Purification and characterization of a recombinant β-galactosidase with transgalactosylation activity from Bifidobacterium infantis HL96

A beta-galactosidase isoenzyme, beta-Gall, from Bifidobacterium infantis HL96, was expressed in Escherichia coli and purified to homogeneity. The molecular mass of the beta-Gall subunit was estimated to be 115 kDa by SDS-PAGE. The enzyme appeared to be a tetramer, with a molecular weight of about 470 kDa by native PAGE. The optimum temperature and pH for o-nitrophenyl-beta-D-galactopyranoside (ONPG) and lactose were 60 degrees C, pH 7.5, and 50 degrees C, pH 7.5, respectively. The enzyme was stable over a pH range of 5.0-8.5, and remained active for more than 80 min at pH 7.0, 50 degrees C. The enzyme activity was significantly increased by reducing agents. Maximum activity required the presence of both Na+ and K+, at a concentration of 10 mM. The enzyme was strongly inhibited by p-chloromercuribenzoic acid, divalent metal cations, and Cr3+, and to a lesser extent by EDTA and urea. The hydrolytic activity using lactose as a substrate was significantly inhibited by galactose. The Km, and Vmax values for ONPG and lactose were 2.6 mM, 262 U/mg, and 73.8 mM, 1.28 U/mg, respectively. beta-Gall possesses strong transgalactosylation activity. The production rate of galactooligosaccharides from 20% lactose at 30 and 60 degrees C was 120 mg/ml, and this rate increased to 190 mg/ml when 30% lactose was used.     

树状多节孢酸性磷酸酶的分离纯化与性质研究

树状多节孢Nodulisporium sylviforme是从东北红豆杉Taxus cuspidata分离、可产生紫杉醇的内生真菌。研究以树状多节孢为材料,利用液体发酵手段获得菌丝体,通过CM-cellulose阴离子交换柱层析、Q-Sepharose阳离子交换柱层析和FPLC凝胶过滤层析（Superdex 75）,获得纯化的树状多节孢酸性磷酸酶蛋白（Nod-ACP）。结合FPLC和SDS-PAGE分析,判定该磷酸酶为分子量44kDa单亚基蛋白。酶学性质研究表明,其最适pH值为3.0,最适温度为58℃。6     

Cloning, expression, and characterization of 5-aminolevulinic acid synthase from Rhodopseudomonas palustris KUGB306

The hemA gene encoding 5-aminolevulinic acid synthase (ALAS) was cloned from the genomic DNA of photosynthetic bacterium Rhodopseudomonas palustris KUGB306. The deduced protein (ALAS) of this gene contained 409 amino acids. The hemA gene was subcloned into an expression vector pGEX-KG and the encoded protein was overexpressed as a fusion protein with glutathione-S-transferase (GST) in Escherichia coli BL21. The recombinant ALAS was purified and isolated free of the fusion partner (GST) by affinity purification on glutathione-Sepharose 4B resin and cleavage of the purified fusion protein by thrombin protease. The optimum pH and temperature of the recombinant ALAS was found to be at pH 7.5-8.0 and 35-40 degrees C, respectively. The Km value of the enzyme was 2.01 mM for glycine and 49.55 microM for succinyl-CoA. The enzyme activity was strongly inhibited by Pb2+, Fe2+, Co2+, Cu2+, and Zn2+ at 1 mM, but slightly affected by Mg2+ and K+. The recombinant ALAS required pyridoxal 5'-phosphate (PLP) as a cofactor for catalysis. Removal of this cofactor led to complete loss of the activity. Ultraviolet-visible spectroscopy with the ALAS suggested the presence of an aldimine linkage between the enzyme and PLP.     

InhA-like protease secreted by Bacillus sp. S17110 inhabited in turban shell

A strain producing a potent protease was isolated from turban shell. The strain was identified as Bacillus sp. S17110 based on phylogenetic analysis. The enzyme was purified from culture supernatant of Bacillus sp. S17110 to homogeneity by ammonium sulfate precipitation, SP-Sepharose, and DEAE-Sepharose anion exchange chromatography. Protease activity of the purified protein against casein was found to be stable at pH 7 to pH 10 and around 50 degrees . Approximately 70% of proteolytic activity of the enzyme was detected either in the presence of 100 mM SDS or Tween 20. The enzyme activity was enhanced in the presence of Ca2+, Zn2+, Mg2+, but was inhibited by EDTA, indicating that it requires metal for its activity. The purified enzyme was found to be a monomeric protein with a molecular mass of 75 kDa, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography. The purified enzyme was analyzed through peptide fingerprint mass spectra generated from matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) and a BLAST search, and identified as immune inhibitor A (inhA) deduced from nucleotide sequence of B. cereus G9241. Since InhA was identified as protease that cleave antibacterial proteins found in insect, inhA-like protease purified from Bacillus sp. S17110 might be pathogenic to sea invertebrates.     

Crystalline L-histidine ammonia-lyase of Achromobacter liquidum. Crystallization and enzymic properties.

Crystalline L-histidine ammonia-lyase of Achromobacter liquidum was prepared with a 24% recovery of the activity. The specific activity of the pure enzyme (63 mumol of urocanic acid min-1 mg-1) is similar to those so far reported for the enzyme from other sources. The purified enzyme appeared to be homogeneous by analytical disc electrophoresis and isoelectric focusing (pI = 4.95). The molecular weight determined by Sephadex G-200 gel filtration is 200000. The optimum pH is 8.2, and the optimum temperature is 50 degrees C. The enzyme showed strict specificity to L-histidine (Km = 3.6 mM). Several histidine derivatives are not susceptible to the enzyme but do inhibit the enzyme activity competitively; the most effective inhibitors are L-histidine methyl ester (Ki = 3.66 mM) and beta-imidazole lactic acid (Ki = 3.84 mM). L-Histidine hydrazide (Ki = 36 mM) and imidazole (Ki = 6 mM) noncompetitively inhibited the enzyme EDTA markedly inhibited enzyme activity and this inhibition were reversed by divalent metal ions such as Mn2+, Co2+ Zn2+, Ni2+, Mg2+, and Ca2+. These results suggest that the presence of divalent metal ions is necessary for the catalytic activity of histidine ammonia-lyase. Sodium borohydride and hydrogen peroxide inhibited the enzyme activity.     

Physiological implications of trehalase from Phaseolus vulgaris root nodules: partial purification and characterization.

The purification and characterization of trehalase from common bean nodules as well as the role of this enzyme on growth, nodulation nitrogen fixation by examining the effects of the trehalase inhibitor validamycin A, was studied. Validamycin A did not affect plant and nodule mass, neither root trehalase and nitrogenase activity; however this treatment applied at the time of sowing increased nodule number about 16% and decreased nodule trehalase activity (16-fold) and the size of nodules. These results suggest that nodule trehalase activity of Phaseolus vulgaris could be involved in nodule formation and development. In addition, acid trehalase (EC 3.2.1.28) was purified from root nodules by fractionating ammonium sulfate, column chromatography on DEAE-sepharose and sephacryl S-300, and finally on native polyacrylamide gel electrophoresis. The purified homogeneous preparation of native acid trehalase exhibited a molecular mass of 42 and 45 kDa on SDS-PAGE. The enzyme has the optimum pH 3.9, Km of 0.109 mM, Vmax of 3630 nkat mg-1 protein and is relatively heat stable. Besides trehalose, it shows maximal activity with sucrose and maltose and, to a lesser degree melibiose, cellobiose and raffinose, and it does not hydrolyze on lactose and turanose. Acid trehalase was activated by Na+, Mn2+, Mg2+, Li+, Co2+, K+ and inhibited by Fe3+, Hg+ and EDTA.     

Isolation of a highly active preparation of beta-D-galactosidase

Methods for isolation and purification of beta-galactosidase from Bacillus subtilis, st. IBP-101 are described. The bacterial cells were disrupted by different procedures such as freezing and thawing with subsequent autolysis at 37 degrees C, disrupting in a French press DKM-3 or in ultrasonic disintegrators UZDN-1 (USSR) and Soniprep-150. It is shown that the specific activity and yield of the enzyme depends to a great extent on the disrupting procedure used. The best results were obtained in case of sonication. The preparation was purified by precipitation with ammonium sulphate (25-75% saturated) and chromatography on DEAE-cellulose and DEAE-Sephadex. The purified enzyme had a specific activity of 3155 units per mg protein. The molecular weight of the homogeneous according to gel polyacrylamide electrophoresis preparation was 215,000, as estimated by gel filtration, and 105,000, as estimated by SDS gel electrophoresis. The enzyme retains the activity in the presence of Na+, Mn2+ or Mg2+ ions or the thiolic reagents, dithiothreitol or 2-mercaptoethanol. The pH optimum of the enzyme activity is 6.3 and it is stable in water solutions at pH from 6 to 9 and can be lyophilized. The given preparation of beta-galactosidase has a high affinity for synthetic substrates such as o- and p-nitrophenyl-beta-D-galactopyranosides and 4-methylumbelliferyl-beta-D-galactopyranoside.     

β-Galactosidase from a cold-adapted bacterium: purification, characterization and application for lactose hydrolysis

The enzyme beta-galactosidase was purified from a cold-adapted organism isolated from Antarctica. The organism was identified as a psychotrophic Pseudoalteromonas sp. The enzyme was purified with high yields by a rapid purification scheme involving extraction in an aqueous two-phase system followed by hydrophobic interaction chromatography and ultrafiltration. The beta-galactosidase was optimally active at pH 9 and at 26 degrees C when assayed with o-nitrophenyl-beta-D-galactopyranoside as substrate for 2 min. The enzyme activity was highly sensitive to temperature above 30 degrees C and was undetectable at 40 degrees C. The cations Na+, K+, Mg2+ and Mn2+ activated the enzyme while Ca2+, Hg2+, Cu2+ and Zn2+ inhibited activity. The shelf life of the pure enzyme at 4 degrees C was significantly enhanced in the presence of 0.1% (w/v) polyethyleneimine. The pure beta-galactosidase was also evaluated for lactose hydrolysis. More than 50% lactose hydrolysis was achieved in 8 h in buffer at an enzyme concentration of 1 U/ml, and was increased to 70% in the presence of 0.1% (w/v) polyethyleneimine. The extent of lactose hydrolysis was 40-50% in milk. The enzyme could be immobilized to Sepharose via different chemistries with 60-70% retention of activity. The immobilized enzyme was more stable and its ability to hydrolyze lactose was similar to that of the soluble enzyme.     

Optimization of culture conditions and properties of immobilized sulfide oxidase from Arthrobacter species

Arthrobacter species strain FR-3, isolated from sediments of a swamp, produced a novel serine-type sulfide oxidase. The production of sulfide oxidase was maximal at pH 7.5 and 30 degrees C. Among various carbon and nitrogen sources tested, glucose and yeast extract were found to be the most effective substrates for the secretion of sulfide oxidase. The sulfide oxidase was purified to homogeneity and the molecular weight of the purified enzyme was 43 kDa when estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified sulfide oxidase can be effectively immobilized in DEAE (diethylaminoethyl)-cellulose matrix with a yield of 66%. The purified free and immobilized enzyme had optimum activity at pH 7.5 and 6.0, respectively. Immobilization increases the stability of the enzyme with respect to temperature. The half-life of the immobilized enzyme was 30 min at 45 degrees C, longer than that of the free enzyme (10 min). The purified free sulfide oxidase activity was completely inhibited by 1 mM Co2+ and Zn2+ and sulfhydryl group reagents (para-chloromercuribenzoic acid and iodoacetic acid). Catalytic activity was not affected by 1 mM Ca2+, Mg2+, Na+ and metal-chelating agent (EDTA).     

N-acetylglutamate 5-phosphotransferase of Pseudomonas aeruginosa. Catalytic and regulatory properties.

Some kinetic properties of N-acetylglutamate 5-phosphotransferase (ATP: N-acetyl-L-glutamate 5-phosphotransferase EC 2.7.2.8) purified approx. 2000-fold from Pseudomonas aeruginosa have been studied. The enzyme required Mg2+ for activity. Mn2+, Zn2+, Co2+, and Ca2+, in this order, could replace Mg2+ partially. The substrate specificity was narrow: N-carbamoyl-L-glutamate and N-formyl-L-glutamate were phosphorylated, but at a lower rate than N-acetyl-L-glutamate; N-propionyl-L-glutamate was almost inactive as a substrate. dATP, but neither GTP nor ITP, could be used instead of ATP. The enzyme had a broad pH optimum from pH 6.5 to 9. Feedback inhibition by L-arginine was markedly dependent on pH. Above pH 9 no inhibition was observed. L-Citrulline was three times less potent an inhibitor than L-arginine. The enzyme showed Michaelis-Menten kinetics, even at low concentration of the second substrate. The apparent Km was 2 mM for N-acetyl-L-glutamate (at 10 mM ATP) and approx. 3 mM for ATP (at 40 mM N-acetyl-L-glutamate). In the presence of L-arginine the rate-concentration curves for N-acetyl-L-glutamate became signoidal, while no cooperativity was detected for ATP. A method was developed allowing the determination of N-acetyl-L-glutamate in the nanomolar range by means of purified enzyme.     

Purification and properties of a heat-stable exoinulinase isoform from Aspergillus fumigatus

An inducible extracellular exoinulinase (isoform II) was purified from the extracellular extract of Aspergillus fumigatus by ammonium sulphate precipitation, followed by successive chromatographies on DEAE-Sephacel, Octyl-Sepharose (HIC), Sephacryl S-200, affinity chromatography on ConA-CL Agarose and Sephacryl S-100 columns. The enzyme was purified 75-folds with 3.2% activity yield from the starting culture broth. The purified isoform II was a monomeric 62 kDa protein with a pI value of 4.5. The enzyme showed maximum activity at pH 6.0 and was stable over a pH range of 4.0-7.0, whereas the optimum temperature for enzyme activity was 60 degrees C. The inulinase isoform II showed exo-inulinolytic activity and retained 72% and 44% residual activity after 12 h at 60 degrees C and 70 degrees C, respectively. The inulin hydrolysis activity was completely abolished with 5 mM Hg2+ and Fe2+, whereas K+ and Cu2+ enhanced the inulinase activity. As compared to sucrose, stachyose and raffinose the purified enzyme had a lower Km (1.25 mM) and higher catalytic center activity (Kcat = 3.47 x 10(4) min(-1)) for inulin. As compared to exoinulinase isoform I of A. fumigatus, purified earlier, the isoform II is more thermostable and is a potential candidate for commercial production of fructose from inulin.     

Purification and characterization of NADPH-dependent Cr(VI) reductase from Escherichia coli ATCC 33456

A soluble Cr(VI) reductase was purified from the cytoplasm of Escherichia coli ATCC 33456. The molecular mass was estimated to be 84 and 42 kDa by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, indicating a dimeric structure. The pI was 4.66, and optimal enzyme activity was obtained at pH 6.5 and 37 degrees C. The most stable condition existed at pH 7.0. The purified enzyme used both NADPH and NADH as electron donors for Cr(VI) reduction, while NADPH was the better, conferring 61%; higher activity than NADH. The Km values for NADPH and NADH were determined to be 47.5 and 17.2 micromol, and the Vmax values 322.2 and 130.7 micromol Cr(VI) min(-1)mg(-1) protein, respectively. The activity was strongly inhibited by N-ethylmalemide, Ag2+, Cd2+, Hg2+, and Zn2+. The antibody against the enzyme showed no immunological cross reaction with those of other Cr(VI) reducing strains.     

Acetyl-coenzyme A carboxylase from the developing endosperm of Ricinus communis. I. Isolation and characterization

Acetyl-coenzyme A carboxylase has been purified from the plastids of developing castor oil seeds. High concentrations of the enzyme are required for stability as well as the presence of dithiothreitol, glycerol, bicarbonate, Triton X-100, and polyvinyl-pyrrolidone. It has a molecular weight of approximately 528,000 and appears to be membrane associated. Acetyl-CoA carboxylase is active over a wide pH range with an optimum at 8.0. Arrhenius plots are biphasic. The enzyme displays normal Michaelis-Menten kinetics with limiting Michaelis constants of KATP, 0.1 mM; KHCO-3, 3.0 mM; and Kacetyl-CoA, 0.05 mM. Monovalent cations, such as K+ and Cs+, exert a small activating effect on the enzyme while a divalent cation, Mn2+ or Mg2+, is essential for activity. The enzyme does not appear to be highly regulated by cellular metabolites.