Dihydrosterigmatocystin and Dihydrodemethylsterigmatocystin,New Metabolites from Aspergillus versicolor

L-Arabinose isomerase (L-arabinose ketol-isomerase, EC 5.3.1.4) was demonstrated from the L-arabinose-grown cells of Streptomyces sp. which was isolated from sea water. The enzyme was purified by MnCl₂ treatment, fractionation by polyethylene glycol and by column chromatographies on Sephadex G-150 and DEAE-cellulose. The purified enzyme was specific only for L-arabinose and the Michaelis constant for L-arabinose was 40 mM at pH 7.5. Manganese or cobalt ions were effective for the enzyme activity after dialysis against EDTA. The enzyme activity was inhibited competitively by L-arabitoI, ribitol and xylitol, of which inhibition constants were 1.1, 1.0, and 15 mM, respectively.     

Studies on the Autolysis of Aspergillus oryzae

Properties of nuclease O, a new intracellular enzyme which was partially purified from autolyzate of Asp. Oryzae,¹⁾ are described in this paper. The purified enzyme preferentially depolymerized RNA and heat denatured DNA, but apparently did not attack native DNA. It was activated by 0.1 mm Mg²⁺ or Mn²⁺, and inactive in the presence of EDTA. Optimum pH of the activity were 7.7 for DNA and 8.2 for RNA. By heat treatment (60°C, 10 min at pH 6) the nuclease completely lost its activity for RNA and DNA. Optimum concentration of Tris buffer for enzymatic activity was 0.15~0.2m.     

Studies on the Autolysis of Aspergillus oryzae

In was found that an intracellular ribonuclease was present as an inactive form in the fresh mycelium of Asp. oryzae. It was about 3 times activated either by 3 m urea or by the autolysis of mycelium at 30°C for 20 hr. The optimum pH of the ribonuclease activity was 8.3. It was heat sensitive (60°C, 10 min), and completely inhibited by 5 mm EDTA. It was activated by 1 mm Mg²⁺ and inhibited by Zn²⁺, Ca²⁺, Cd²⁺, Co²⁺ and Cu²⁺.     

Purification and Properties of Alkaline Proteinase from Aspergillus oryzae

Alkaline proteinase was purified from culture extract of a strain of Aspergillus oryzae. The process consists of the Amberlite IRC-50 adsorption, column chromatography on DEAE-cellulose and CM-cellulose and Sephadex G-100 gel filtration. The molecular weight of the enzyme was estimated to be about 23,000 by a gel filtration method. Alkaline proteinase showed neither carboxypeptidase activity nor aminopeptidase activity, but degraded 10101010 poly-l,α-glutamic acid, poly-l-lysine, 10101010 and 10101010. The enzyme was completely inhibited by diisopropylphos-phorofluoridate (10^?2 m) or potato inhibitor (250 μg/ml).     

Substrate Specificity of Alkaline Proteinases from Aspergillus sydowi and Aspergillus sulphureus

l-Fucose (l-galactose) dehydrogenase was isolated to homogeneity from a cell-free extract of Pseudomonas sp. No 1143 and purified about 380-fold with a yield of 23 %. The purification procedures were: treatment with polyethyleneimine, ammonium sulfate fractionation, chromatographies on phenyl-Sepharose and DEAE-Sephadex, preparative polyacrylamide gel electrophoresis, and gel filtration on Sephadex G-100. The enzyme had a molecular weight of about 34,000. The optimum pH was at 9 — 10.5 and the isoelectric point was at pH 5.1. l-Fucose and l-galactose were effective substrates for the enzyme reaction, but d-arabinose was not so much. The anomeric requirement of the enzyme to l-fucose was the β-pyranose form, and the reaction product from l-fucose was l-fucono- lactone. The hydrogen acceptor for the enzyme reaction wasNADP⁺, and NAD ⁺ could be substituted for it to a very small degree. Km values were 1.9mm, 19mm, 0.016mm, and 5.6mm for l-fucose, l- galactose, NADP⁺, and NAD⁺, respectively. The enzyme activity was strongly inhibited by Hg^{2 +}, Cd^{2 +}, and PCMB, but metal-chelating reagents had almost no effect. In a preliminary experiment, it was indicated that the enzyme may be usable for the measurement of l-fucose.     

Studies on the Acid-Protease of Paecilomyces varioti Bainier TPR-220

The acid-protease of Paecilomyces varioti Bainier TPR-220 can hydrolyze carbobenzoxy-l-glutamyl-l-tyrosine, which is the substrate for pepsin, the acid-protease of Aspegillus saitoi by Yoshida and of Asp. oryzae by Nunokawa, and the trypsinogenkinase by Nakanishi, and benzoyl-l-argininamide, which is the substrate for trypsin, papain, and above two acid-proteases, optimally at pH 3.5 and 5.5 at 45°C, respectively. The Michaelis constant and activation energy of the enzyme are 4.08 × 10^-3m and 9.17 × 10³ cal/mol for the former, and 6.58 × 10^-3m and 6.86 × 10³ cal/mol for the latter, respectively.

Other substrates for papain, chymotrypsin, and various exopeptidases are hardly hydrolyzed by the enzyme.     

Purification and Characterization of Novel N-Acyl-D-aspartate Amidohydrolase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6

Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) produced N-acyl-D-aspartate amidohydrolase (D-AAase) in the presence of N-acetyl-D-aspartate as an inducer. The enzyme was purified to homogeneity. The enzyme had a molecular mass of 56 kDa and was shown by sodium dodecyl sulfate (SDS)–polyacrylamide gel electrophoresis (PAGE) to be a monomer. The isoelectric point was 4.8. The enzyme had maximal activity at pH 7.5 to 8.0 and 50°C, and was stable at pH 8.0 and up to 45°C. N-Formyl (K_m=12.5 mM), N-acetyl (K_m=2.52 mM), N-propionyl (K_m=0.194 mM), N-butyryl (K_m=0.033 mM), and N-glycyl (K_m =1.11 mM) derivatives of D-aspartate were hydrolyzed, but N-carbobenzoyl-D-aspartate, N-acetyl-L-aspartate, and N-acetyl-D-glutamate were not substrates. The enzyme was inhibited by both divalent cations (Hg²⁺, Ni²⁺, Cu²⁺) and thiol reagents (N-ethylmaleimide, iodoacetic acid, dithiothreitol, and p-chloromercuribenzoic acid). The N-terminal amino acid sequence and amino acid composition were analyzed.     

Inhibition of l-Alanine Adding Enzyme by Glycine

l-Alanine adding enzymes from Bacillus subtilis and Bacillus cereus which catalyzed l-alanine incorporation into UDPMurNAc were partially purified and the properties of the enzymes were examined. The enzyme from B. subtilis was markedly stimulated by reducing agents including 2-mercaptoethanol, dithiothreitol, glutathione and cysteine. Mn²⁺ and Mg²⁺ activated l-alanine adding activity and their optimal concentrations were 2 to 5 mm and 10 mm, respectively. The optimum pH was 9.5 and the Km for l-alanine was 1.8×10^?4m. l-Alanine adding reaction was strongly inhibited by p-chloromercuribenzoate and N-ethyl-maleimide. Among glycine, l- and d-amino acids and glycine derivatives, glycine was the most effective inhibitor of the l-alanine adding reaction. The enzyme from B. cereus was more resistant to glycine than that from B. subtilis. Glycine was incorporated into UDPMurNAc in place of l-alanine, and the Ki for glycine was 4.2×l0^?3m with the enzyme from B. subtilis. From these data, the growth inhibition of bacteria by glycine is discussed.     

d-Gluconate Dehydrogenase, 2-Keto-d-gluconate Yielding,from Gluconobacter dioxyacetonicus: Purification and Characterization

d-Gluconate dehydrogenase catalyzing the oxidation of d-gluconate to 2-keto-d-gluconate was solubilized with Triton X-100 from the membrane of Gluconobacter dioxyacetonicus IFO 3271 and purified to an almost homogeneous state by chromatographies on DEAE-cellulose and CM-Toyopearl in the presence of 0.1% Triton X-100. The enzyme had three subunits with molecular weights of 64,000, 45,000 and 21,000, and contained approximately 2 mol of heme per mol of the enzyme. The prosthetic group of the dehydrogenase was found to be a flavin covalently bound to the enzyme protein. The substrate specificity of the purified enzyme was very strict for d-gluconate and the apparent Michaelis constant for d-gluconate was 2.2 mm. The optimum pH and temperature of the purified enzyme were 6.0 and 40°C, respectively.     

Identification of Arsenobetaine as a Major Arsenic Compound in the Ivory Shell Buccinum striatissimum

A restriction endonuclease, designated as DmaI, was purified from cell-free extracts of Deleya marina IAM 14114 by streptomycin treatment, ammonium sulfate fractionation and two steps of chromatographies on heparin-Sepharose CL-6B and Mono Q (HR 5/5, FPLC). The purified enzyme was homogeneous on SDS-polyacrylamide gel disk electrophoresis and a ligation-recutting test. The relative molecular mass measurements of the purified enzyme gave 28,000 daltons by SDS-polyacrylamide gel disk electrophoresis and 56,000 daltons by gel filtration. These data indicated that the purified enzyme (56,000 daltons) has a dimeric structure composed of two 28,000-dalton subunits. The isoelectric point was 5.5. The purified enzyme worked best at 37°C in a reaction mixture (50 μl) containing 1.0 μg λDNA, 10 mm Tris–HCl, 7 mm 2-mercaptoethanol, 7 mm MgCl₂ and 100 mm NaCl (pH 7.5). The enzyme was stable up to 55°C and between pH 7.0 and 9.0. The purified enzyme recognizes the palindromic hexanucleotide DNA sequence 5′-CAGCTG-3′, cuts between G and C and produces a flush end (isoschizomer of PvuII).     

Branched Chain Amino Acid Aminotransferase of Pseudomonas sp

Branched chain amino acid aminotransferase was partially purified from Pseudomonas sp. by ammonium sulfate fractionation, aminohexyl-agarose and Bio-Gel A-0.5 m column chromatography.

This enzyme showed different substrate specificity from those of other origins, namely lower reactivity for l-isoleucine and higher reactivity for l-methionine.

Km values at pH 8.0 were calculated to be 0.3 mm for l-leucine, 0.3 mm for α-ketoglutarate, 1.1 mm for α-ketoisocaproate and 3.2 mm for l-glutamate.

This enzyme was activated with β-mercaptoethanol, and this activated enzyme had different kinetic properties from unactivated enzyme, namely, Km values at pH 8.0 were calculated to be 1.2 mm for l-leucine, 0.3 mm for α-ketoglutarate.

Isocaproic acid which is the substrate analog of l-leucine was competitive inhibitor for pyridoxal form of unactivated and activated enzymes, and inhibitor constants were estimated to be 6 mm and 14 mm, respectively.     

NADP-Specific Glutamate Dehydrogenase from Alkaliphilic Bacillus sp. KSM-635: Purification and Enzymatic Properties

An NADP-specific glutamate dehydrogenase [L-glutamate: NADP⁺ oxidoreductase (deaminating), EC 1.4.1.4] from alkaliphilic Bacillus sp. KSM-635 was purified 5840-fold to homogeneity by a several-step procedure involving Red-Toyopearl affinity chromatography. The native protein, with an isoelectric point of pH 4.87, had a molecular mass of approximately 315 kDa consisting of six identical summits each with a molecular mass of 52 kDa. The pH optima for the aminating and deaminating reactions were 7.5 and 8.5, respectively. The optimum temperature was around 60°C for both. The purified enzyme had a specific activity of 416units/mg protein for the aminating reaction, being over 20-fold greater than that for deaminating reaction, at the respective pH optima and at 30°C. The enzyme was specific for NADPH (K_m 44 μM), 2-oxoglutarate (K_m 3.13 mM), NADP⁺ (K_m 29 μM), and L-glutamate (K_m 6.06 mM). The K_m for NH₄Cl was 5.96 mM. The enzyme could be stored without appreciable loss of enzyme activity at 5°C for half a year in phosphate buffer (pH 7.0) containing 2 mM 2-mercaptoethanol, although the enzyme activity was abolished within 20 h by freezing at ?20°C.     

Functional Characterization of D-Galacturonic Acid Reductase,a Key Enzyme of the Ascorbate Biosynthesis Pathway,from Euglena gracilis

D-Galacturonic acid reductase, a key enzyme in ascorbate biosynthesis, was purified to homogeneity from Euglena gracilis. The enzyme was a monomer with a molecular mass of 38–39 kDa, as judged by SDS–PAGE and gel filtration. Apparently it utilized NADPH with a Km value of 62.5±4.5 μM and uronic acids, such as D-galacturonic acid (Km=3.79±0.5 mM) and D-glucuronic acid (Km=4.67±0.6 mM). It failed to catalyze the reverse reaction with L-galactonic acid and NADP⁺. The optimal pH for the reduction of D-galacturonic acid was 7.2. The enzyme was activated 45.6% by 0.1 mM H₂O₂, suggesting that enzyme activity is regulated by cellular redox status. No feedback regulation of the enzyme activity by L-galactono-1,4-lactone or ascorbate was observed. N-terminal amino acid sequence analysis revealed that the enzyme is closely related to the malate dehydrogenase families.     

An Improved Assay Method for Antifouling Substances Using the Blue Mussel,Mytilus edulis

The restriction endonuclease AatII was purified from cell-free extracts of Acetobacter aceti IFO 3281 by streptomycin treatment, ammonium sulfate fractionation, combined column chromatographies on DEAE-Toyopearl 650S, heparin-Sepharose CL-6B and DEAE-Sepharose CL-6B and FPLC on Mono Q and on Superose 12 (gel filtration). The purified enzyme was homogeneous on SDS-polyacrylamide gel disk electrophoresis. The relative molecular mass of the purified enzyme was 190,000 daltons by gel filtration. The SDS-polyacrylamide gel disk electrophoresis gave the relative molecular mass of 47,500 daltons. These data indicated that the purified, native enzyme is a tetramer (190,000 daltons) composed of four 47,500-dalton subunits. The isoelectric point of the enzyme was 6.0. The purified enzyme was intensely activated by manganese ion (50-fold increase or more when compared with magnesium ion). The enzyme worked best at 37°C and pH 8.5 in a reaction mixture (50 μl) containing 1.0 μg λDNA, 10 mm Tris-HCl, 7 mm 2-mercaptoethanol, 7 mm MnCl₂ and 50 mm NaCl. The enzyme recognizes the same palindromic hexanucleotide sequence 5′-GACGTC-3′, cuts between T and C and produces a 3′-tetranucleotide extension in the presence of MnCl₂, as it does in the presence of MgCl₂.     

Biosynthetic Threonine Deaminase from Proteus morganii

Biosynthetic threonine deaminase was purified to an apparent homogeneous state from the cell extract of Proteus morganii, with an overall yield of 7.5%. The enzyme had a s⁰_20,w of 10.0 S, and the molecular weight was calculated to be approximately, 228,000. The molecular weight of a subunit of the enzyme was estimated to be 58,000 by sodium dodecyl sulfate gel electrophoresis. The enzyme seemed to have a tetrameric structure consisting of identical subunits. The enzyme had a marked yellow color with an absorption maximum at 415 nm and contained 2 mol of pyridoxal 5′-phosphate per mol. The threonine deaminase catalyzed the deamination of l-threonine, l-serine, l-cysteine and β-chloro-l-alanine. Km values for l-threonine and l-serine were 3.2 and 7.1 mm, respectively. The enzyme was not activated by AMP, ADP and ATP, but was inhibited by l-isoleucine. The Ki for l-isoleucine was 1.17 mm, and the inhibition was not recovered by l-valine. Treatment with mercuric chloride effectively protected the enzyme from inhibition by l-isoleucine.     

Purification and Characterization of Glutamate Decarboxylase from Lactobadllus bvevis IFO 12005

Glutamate decarboxylase (GAD) [EC 4.1.1.15] was purified from a cell-free extract of Lactobadllus brevis TFO 12005 by chromatographies on Sephadex G-100, DEAE-Sepharose CL-6B, and Mono Q. About 9 mg of purified GAD was obtained from 90.2 g of wet cells. The purified preparation showed a single protein band on SDS-PAGE. The molecular weights of purified GAD by SDS-PAGE and gel filtration on Superdex 200 were 60,000 and 120,000, respectively, indicating that GAD from L. brevis exists as a dimer. The N-terminal amino acid sequence of the purified GAD was NH₂-Met-Asn-Lys-Asn-Asp-Gln-Glu-Gln-Thr-. The optimum pH and temperature of GAD were at pH 4.2 and at 30°C. The GAD activity was increased by the addition of sulfate ions in a dose-dependent manner. The order of effect was as follows: ammonium sulfate?>?sodium sulfate?>?magnesium sulfate, indicating that the increase of hydrophobic interaction between subunits causes the increase of GAD activity. The purified GAD reacted only with l-glutamic acid as a substrate and the K_m, k_cat, and k_cat/K_m values were 9.3 mm, 6.5 s^?1, and 7 × 10² m^?1 s^?1, respectively.     

Characterization of a Cellobiose Phosphorylase from a Hyperthermophilic Eubacterium,Thermotoga maritima MSB8

The cepA putative gene encoding a cellobiose phosphorylase of Thermotoga maritima MSB8 was cloned, expressed in Escherichia coli BL21-codonplus-RIL and characterized in detail. The maximal enzyme activity was observed at pH 6.2 and 80°C. The energy of activation was 74 kJ/mol. The enzyme was stable for 30 min at 70°C in the pH range of 6-8. The enzyme phosphorolyzed cellobiose in an random-ordered bi bi mechanism with the random binding of cellobiose and phosphate followed by the ordered release of D-glucose and α-D-glucose-1-phosphate. The K _m for cellobiose and phosphate were 0.29 and 0.15 mM respectively, and the k _cat was 5.4 s^-1. In the synthetic reaction, D-glucose, D-mannose, 2-deoxy-D-glucose, D-glucosamine, D-xylose, and 6-deoxy-D-glucose were found to act as glucosyl acceptors. Methyl-β-D-glucoside also acted as a substrate for the enzyme and is reported here for the first time as a substrate for cellobiose phosphorylases. D-Xylose had the highest (40 s^-1) k _cat followed by 6-deoxy-D-glucose (17 s^-1) and 2-deoxy-D-glucose (16 s^-1). The natural substrate, D-glucose with the k _cat of 8.0 s^-1 had the highest (1.1×10⁴ M^-1 s^-1) k _cat/K _m compared with other glucosyl acceptors. D-Glucose, a substrate of cellobiose phosphorylase, acted as a competitive inhibitor of the other substrate, α-D-glucose-1-phosphate, at higher concentrations.     

Partial Purification and Characterization of Polyphenol Oxidase Isozymes in Banana Bud

Polyphenol oxidase was extracted from banana buds in the presences of Triton X-100, isoascorbate, and Polyclar AT, and two isozymes I and II have been separated and partially purified by chromatographies on Butyl Toyopearl 650 and DEAE-cellulose. I and II had different mobility in polyacrylamide gel electrophoresis with optimum pHs of 6.8 and 5.5, respectively. Both enzymes showed the apparent K_m values of 0.5 mM for dopamine with substrate inhibitions at its higher concentrations. I and II were inhibited competitively by NaCI with the K_i values of 140 mM and 40 mM, respectively. I and II have a high heat stability, and 88 and 95% of the initial activities were retained after 1-hr incubation at 70°C, respectively.     

Purification and Characterization of β-D-Glucosidase (β-D-Fucosidase) from Bifidobacterium breve clb Acclimated to Cellobiose

The β-d-glucosidase (EC. 3.2.1.21) activity of Bifidobacterium breve 203 was increased by acclimation with cellobiose, and the enzyme was purified to homogeneity from cell-free extracts of an acclimatized strain of B. breve clb, by ammonium sulfate fractionation and column chromatographies of anion-exchange, gel filtration, Gigapaite, and hydrophobic interaction. This enzyme had not only β- d-glucosidase activity but also β- d-fucosidase activity, which is specific to Bifidobacteria in intestinal flora. The molecular weight of the purified enzyme was estimated to be 47,000–48,000 and the enzyme was assumed to be a monomeric protein. The optimum pH and temperature of the enzyme were around 5.5 and 45°C, respectively. The enzyme was stable up to 40°C and between pH 5 and 8. The isoelectric point of the enzyme was 4.3 and the K_m values for p-nitrophenyl-β-d-glucoside and p-nitrophenyl-β-d-fucoside were 1.3mm and 0.7 mm, respectively. This enzyme had also transferase activity for the β-d-fucosyl group but not for the β-d-glucosyl group. The N-terminal amino acid sequence of this enzyme was similar to those of β-d-glucosidase from other bacteria, actinomycetes, and plants.     

Purification and Characterization of β-N-Acetylhexosaminidase from the Liver Prawn,Penaeus japonicus

β-N-Acetvlhexosaminidase (EC 3.2.1.52) was purified from the liver of a prawn, Penaeus japonicus, by ammonium sulfate fractionation and chromatography with Sephadex G-100, hydroxylapatite, DEAE-Cellulofine, and Cellulofine GCL-2000-m. The purified enzyme showed a single band keeping the potential activity on both native PAGE and SDS–PAGE. The apparent molecular weight was 64,000 and 110,000 by SDS–PAGE and gel filtration, respectively. The pI was less than 3.2 by chromatofocusing. The aminoterminal amino acid sequence was NH₂-Thr-Leu-Pro-Pro-Pro-Trp-Gly-Trp-Ala-?-Asp-Gln-Gly-VaI-?-Val-Lys-Gly-Glu-Pro-. The optimum pH and temperature were 5.0 to 5.5 and 50°C, respectively. The enzyme was stable from pH 4 to 11, and below 55°C. It was 39% inhibited by 10mM HgCl₂.

Steady-state kinetic analysis was done with the purified enzyme using N-acetylchitooligosaccharides (GlcNAc_n, n = 2 to 6) and p-nitrophenyl N-acetylchitooligosaccharides (pNp-β-GlcNAc_n, n= 1 to 3) as the substrates. The enzyme hydrolyzed all of these substrates to release monomeric GlcNAc from the non-reducing end of the substrate. The parameters of K_m and k_cat at 25°C and pH 5.5 were 0.137 mM and 598s^–1 for pNp-β-GlcNAc, 0.117 mM and 298s^–1 for GlcNAc₂, 0.055 mM and 96.4s^–1 for GlcNAc₃, 0.044 mM and 30.1 s^–1 for GlcNAc_4, 0.045 mM and 14.7 s^–1 for GlcNAc₅, and 0.047 mM and 8.3 s^–1 for GlcNAc₆, respectively. These results suggest that this β-N-acetylhexosaminidase is an exo-type hydrolytic enzyme involved in chitin degradation, and prefers the shorter substrates.