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Biomedical subjects

A Endo

Publications and source records attributed to A Endo.

At least 307 records · Page 17Linked to original sources
PubMed1977

Time-dependent, irreversible inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase by the antibiotic citrinin.

The inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase by citrinin, an antibiotic, has been studied. The inhibition was the mixed type with respect to 3-hydroxy-3-methylglutaryl-CoA and non-competitive with respect to NADPH. When the enzyme was preincubated with citrinin prior to enzyme assay, however, it caused a time-dependent, irreversible inhibition, possibly by binding to a site distinct from the active center on the enzyme protein.

Alcohol Oxidoreductases↗
PubMed1977

Inhibition of sterol synthesis by citrinin in a cell-free system from rat liver and yeast.

Citrinin, a fungal metabolite known as an antibiotic, strongly inhibited the labeled acetate incorporation into nonsaponifiable lipids by a cell-free system from rat liver but not the labeled mevalonate incorporation. Of the enzymes involved in cholesterol synthesis, two enzymes, acetoacetyl-CoA thiolase (EC 2.3.1.9) and 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.34), were specifically inhibited by the antibiotic. The concentration required for 50% inhibition was 0.2 mM for the former enzyme and 0.5 mM for the latter. Essentially the same results were obtained with a cell-free system from yeast although higher concentrations of the antibiotic were required for inhibition.

Acetyl-CoA C-Acetyltransferase↗
PubMed1977

Extracellular acid protease of Aspergillus oryzae grown on liquid media: multiple forms due to association with heterogeneous polysaccharides.

The acid protease (EC 2.4.23.6) that is produced extracellularly when Aspergillus oryzae is grown on liquid media has been isolated and characterized. The enzyme was purified by precipitation with tannic acid, chromatography on Duolite A-2, and gel filtration on Sephadex G-100. The last step yielded four active components, with varying molecular weights ranging from 42,000 to 60,000. Two of them, designated E1 and E1a, with molecular weights of 60,000 and 55,000, respectively, were heterogeneous on isoelectric focusing, both giving at least three enzyme species with different isoelectric points, whereas the other two, E1b and E2, with molecular weights of 49,000 and 42,000, respectively, were essentially homogeneous. These four enzymes activated bovine pancreatic trypsinogen and had the same pH optima in the acid pH range. They had essentially the same amino acid composition and immunologically cross-reacted with each other. These catalytic, chemical, and immunological properties are similar to those of acid protease A1 and A2 from A. oryzae grown on solid bran media. Unlike acid protease from solid bran culture, which contains both carbohydrate-containing and the carbohydrate-free species, all of the four enzymes, E1, E1a, E1b, and E2, contained carbohydrate, ranging from 18.9 to 43% and comprising three hexoses, glucose, galactose, and mannose. The carbohydrate portions were polysaccharide in nature and heterogeneous with respect to both molecular weight and sugar composition, and at least a part of the carbohydrate was present in the form of homopolysaccharides such as galactan and mannan. These findings indicate that polysaccharide chains with different molecular weights and with different chemical compositions are apparently responsible for the microheterogeneity of acid protease.

Amino Acids↗
PubMed1976

Purification and characterization of the two molecular forms of Aspergillus oryzae acid protease.

The isolation and partial characterization of the acid proteases A1 and A2 (EC3.4.23.6) from Aspergillus oryzae grown on solid bran culture are described. The purified preparations were essentially homogeneous by several criteria including sedimentation analysis and polyacrylamide gel electrophoresis. The physiochemical properties of the proteases A1 and A2 were as follows (in the order: A1, A2): molecular weight: 63 000 & 32 000; sedimentation coefficient s20, w: 3.93 and 3.16 S; diffusion constant D20, w, 5.63 - 10(-7) and 8.61 - 10(-7) CM2/S, partial specific volume, v: 0.73 ml/g for both; nitrogen content: 16.30 and 13.42%; E1% 1 cm at 280 nm: 5.9 and 11.1. The two enzymes had the same pH optima in the acid pH range, and both activated bovine pancreatic trypsinogen. The enzymes were essentially of the same amino acid composition and immunologically cross-reacted with each other. The protease A2 contained little or no carbohydrate, whereas the protease A1 was glycoprotein, containing 49% carbohydrate comprising glucose, mannose, and galactose. These results suggest that the protein portion of acid protease A1 is the same as that of acid protease A2.

Amino Acids↗
PubMed1976

Inhibition of in vitro cholesterol synthesis by fatty acids.

Inhibitory effect of 44 species of fatty acids on cholesterol synthesis has been examined with a rat liver enzyme system. In the case of saturated fatty acids, the inhibitory activity increased with chain length to a maximum at 11 to 14 carbons, after which activity decreased rapidly. The inhibition increased with the degree of unsaturation of fatty acids. Introduction of a hydroxy group at the alpha-position of fatty acids abolished the inhibition, while the inhibition was enhanced by the presence of a hydroxy group located in an intermediate position of the chain. Branched chain fatty acids having a methyl group at the terminal showed much higher activity than the corresponding saturated straight chain fatty acids with the same number of carbons. With respect to the mechanism for inhibition, tridecanoate was found to inhibit acetoacetyl-CoA thiolase specifically without affecting the other reaction steps in the cholesterol synthetic pathway. The highly unsaturated fatty acids, arachidonate and linoleate, were specific inhibitors of 3-hydroxy-3-methyl-glutaryl-CoA synthase. On the other hand, ricinoleate (hydroxy acid) and phytanate (branched-chain acid) diminished the conversion of mevalonate to sterols by inhibiting a step or steps between squalene and lanosterol.

Acetates↗