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.     

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.     

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.     

Effect of 1-Anilino-8-naphthalenesulfonate on Properties and Associations of αs-, β- and κ-Caseins

It was indicated from fluorescence spectra and fluorescence titration that a hydrophobic probe, 1-anilino-8-naphthalenesulfonate (ANS), binds to casein components (α_s-, β- and κ-caseins). Fluorescence intensity and affinity of ANS-κ-casein complex were larger than that of ANS-α_s- and ANS-β-casein complexes. Enhancements of fluorescence intensity of complexes of casein components were observed by the addition of KCI or CaCl₂. Reason for the enhancement was postulated to be the increase of the quantum yield of the ANS fluorescence caused by the environmental change of ANS binding region of the casein components.

Marked increase of sedimentation coefficient of β-casein in the presence of KCl or CaCl₂ at 10°C was caused by the addition of ANS. This may be responsible for the stimulation of the Ca-dependent precipitation of β-casein by the addition of ANS.

It was found that α_s · κ-association was prevented by ANS and that hydrophobic interaction have an important role for α_s · κ-association.     

One-step Purification of Guinea Pig Liver Transglutaminase Using a Monoclonal-antibody Immunoadsorbent

Guinea pig liver transglutaminase was purified in a yield of more than 80% by a one-step purification procedure using an immunoadsorbent column of monoclonal antibodies. Active enzyme could be recovered by alkaline buffer desorption and quick neutralization. The purified enzyme was more than 98% homogeneous on Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, and had the same enzymological and immunological properties as those of the enzyme purified by conventional procedures.