Changes of Hydrolytic Activities of Buckwheat α-Glucosidase by Acetylation with N-Acetylimidazole

A treatment of buckwheat α-glucosidase with N-acetylimidazole brought about the acétylation of 6.4 tyrosyl residues, 0.38 free sulfhydryl groups and about 50% of free amino groups, and the decrease in the hydrolytic activities toward maltooligosaccharides (G₂~G₈, G13) and soluble starch. The affinities for the substrate other than maltose were diminished by the modification and the extent of the reduction of the affinities was apparently dependent on the degree of polymerization of maltooligosaccharides, while the affinity for phenyl α- maltoside was increased. The treatment of the acetylated enzyme with hydroxylamine resulted in the complete restration of the affinities for all substrates tested. It seems that these facts were due to the acétylation of several tyrosyl residues located in or near certain subsites of the enzyme. About 25 % of the hydrolytic activity remained inert in spite of the deacetylation with hydroxylamine, which was assumed to be attributed to the partial modification of free sulfhydryl group localized closely near the catalytic site of the enzyme.     

Successive Isolation of Proteinase Hyperproductive Mutants of Aspergillus sojae

Hydrochloric acid treatment of methyl 3-(4-isobutylphenyl)-3-methylglycidate and methyl 2-hydroxy-3-(4-isobutylphenyl)-3-butenoate, a rearrangement product of the former, in acetic acid gave 3-(4-isobutylphenyl)-3-methylpyruvic acid and 2-(4-isobutylphenyl)-pro-panal. The same treatment of 2-hydroxy-3-(4-isobutylphenyl)-3-butenoic acid gave 2-(4-isobutylphenyl)-propanal. Both 3-(4-isobutylphenyl)-3-methylpyruvic acid and 2-(4-iso-butylphenyl)-propanal were oxidized to 2-(4-isobutylphenyl)-propionic acid.     

Polyacrylamide Gel Disc Electrophoresis of Alkaline Proteinases from Aspergillus Species

Ciliatine (2-aminoethylphosphonic acid) (76 mg) was isolated from 72 g of lipids of the oyster with a combination of ion exchange chromatographic techniques and was identified from the results of elementary analysis, infrared spectrum, and chromatographic behaviors. The phosphonic acid was also detected in hydrolysates of a chloroform-methanol insoluble fraction of the oyster. It has been demonstrated that the oyster contains high concentration of ciliatine.     

Purification and Some Properties of Flint Corn α-Glucosidase

An α-glucosidase was purified from flint corn by precipitation with ammonium sulfate, chromatographies on CM-cellulose and Hydroxylapatite and gel-filtrations on Sephadex G-100. The purified enzyme was homogeneous in ultracentrifugal and disc electrophoretic analysis. The sedimentation coefficient was calculated to be 6.5 S. The molecular weight was estimated to be approximately 6.5×10⁴ by gel-filtration technique.

The optimal pH was found to be 3.6 for both maltose and soluble starch. The enzyme lost about 80% of the activity by incubation at 60°C for 10 min.

The ratio of velocity of hydrolysis for maltose, phenyl-α-glucoside and soluble starch was estimated to be 100:14.3:6.1 in this order. The αglucosidase hydrolyzed soluble starch exo-wisely.     

A New Metabolite, 6-Oxo-7-azatridecanedioic Acid,a Microbial Product from Cyclic Dimer of ε-Caprolactam

A series of partially and heterogeneously N-acylated chitosans was prepared and isolated in 50 ~ 100% yields. The structure of N-acyl groups influenced the gelation. The minimum requirement for the gelation was defined as ca. 0.4 N-lauroyl (C₁₂), ca. 0.6 N-fatty acyl (C₃–C₁₀) or ca. 0.7 N-benzoyl groups per hexosaminide residue. However, the gelation did not occur with N-high fatty acyl (C₁₄-C₁₈) groups.1)     

Subunits and Sulfhydryl Groups of Beef Liver d-Glycerate Dehydrogenase

The amino acid composition of beef liver d-glycerate dehydrogenase (EC 1.1.1.29) was determined. Results of sodium dodecyl sulfate gel electrophoresis and measurements of the number of NADH bound by the enzyme and the number of the essential sulfhydryl groups suggested that the enzyme was composed of two identical subunits with the molecular weight of 36,000. Close relation between the essential sulfhydryl groups and the coenzyme binding site was also suggested. Effect of an alkylating agent (bromopyruvate) with the structure similar to the substrate was studied. Effects of iodoacetate and iodoacetamide were also studied. It was suggested that these reagents behaved as active-site-directed irreversible inhibitors of the enzyme. Bromopyruvate exhibited a high affinity to the enzyme. Iodoacetate (anionic reagent) had a higher affinity than iodoacetamide (neutral reagent).     

Multiple Forms of Rice Seeds β-Amylases on Zymogram

Hen lysozyme modified with histamine (HML) and Japanese quail lysozyme (JQL) were treated with immobilized metal ion affinity chromatography to analyze the states of their imidazole groups. When Ni(II) was used as the metal ion immobilized, JQL was strongly retained in a Ni(II)-chelating Sepharose column, while hen lysozyme and HML were hardly retained in the same column. All of these lysozymes have a histidine imidazole group at the 15th position, while JQL has an additional histidine imidazole group at the 103rd position and HML has an additional imidazole group covalently attached to Asp101. Thus, I concluded that the imidazole group at the 103rd position of JQL is exposed to the solvent and recognized by the metal ion, but that the imidazole group attached to Asp101 in HML is localized to a hydrophobic region and not recognized by the metal ion.     

Carbohydrate and Amino Acid Composition of α-Glucosidase from Saccharomyces logos

A water-soluble and neutral polysaccharide was extracted from the current pseudobulbs of Oncidium “Gower Ramsey” during the early inflorescence stage (flower stalk less than 4 cm) by hot water, precipitated with ethanol, and purified with an anion exchanger. From the data of monosaccharide composition and linkage and anomeric configuration analyses, the polysaccharide was identified as a linear β-1→4 linked mannan.