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Biomedical subjects

R Kido

Publications and source records attributed to R Kido.

At least 109 records · Page 6Linked to original sources
PubMed1976

Identity of isoenzyme 1 of histidine-pyruvate aminotransferase with serine-pyruvate aminotransferase.

After glucagon injection, rats showed virtually identical percentage increases in hepatic histidine-pyruvate aminotransferase and serine-pyruvate aminotransferase activities, both in the mitochondria and in the cytosol. Histidine-pyruvate aminotransferase isoenzyme 1, with pI8.0, was purified to homogeneity from the mitochondrial fraction of liver from glucagon-injected rats. The purified enzyme catalysed transamination between a number of amino acids and pyruvate or phenylpyruvate. For transamination with pyruvate, the activity with serine reached a constant ratio to that with histidine during purification, which was unchanged by a variety of treatments of the purified enzyme. Serine was found to act as a competitive inhibitor of histidine transamination, and histidine of serine transamination. These results suggest that histidine-pyruvate amino-transferase isoenzymes 1 is identical with serine-pyruvate aminotransferase. The enzyme is probably composed of two identical subunits with mol. wt. approx. 38000. The absorbance maximum at 410 nm and the inhibition by carbonyl reagents strongly indicate the presence of pyridoxal phosphate.

Animals↗
PubMed1976

Organ distribution of rat histidine-pyruvate aminotransferase isoenzymes.

The organ distribution of rat histidine-pyruvate aminotransferase isoenzymes 1 and 2 was examined by using an isoelectric-focusing technique. Isoenzyme 1 (pI8.0) is present only in the liver and its activity is increased by the injection of glucagon, whereas isoenzyme 2 (pI5.2) is distributed in all tissues (liver, kidney, brain and heart) tested, and is not affected by glucagon injection. Isoenzyme 2 of the liver, kidney, brain and heart was purified by the same procedure and characterized. Isoenzyme 2 preparations from these four tissues were nearly identical in physical and enzymic properties. These properties differed from those previously found for the highly purified isoenzyme 1 preparation of rat liver. Isoenzyme 2 was active with pyruvate but not with 2-oxoglutarate as amino acceptor. Amino donors were effective in the following order of activity: tyrosine greater than histidine greater than phenylalanine greater than kynurenine greater than tryptophan. Very little activity was found with 5-hydroxytryptophan. The apparent Km for histidine was about 0.45 mM. The Km for pyruvate was about 4.5 mM with histidine as amino donor. The amino-transferase activities of isoenzyme 2 towards phenylalanine and tyrosine were inhibited by histidine. The ratio of aminotransferase activities towards these three amino acids was constant through gel filtration, electrophoresis, isoelectric focusing and sucrose-density-gradient centrifugation of the purified isoenzyme 2 preparations. These results suggest that these three activities are properties of the same enzyme protein. Sephadex G-150 gel filtration and sucrose-density-gradient centrifugation yielded mol.wts. of approx. 95000 and 92000 respectively. The pH optimum was between 9.0 and 9.3.

Animals↗
PubMed1976

Purification, characterization and identification of rat liver histidine-pyruvate aminotransferase isoenzymes.

1. Histidine-pyruvate aminotransferase (isoenzyme 1) was purified to homogeneity from the mitochondrial and supernatant fractions of rat liver, as judged by polyacrylamide-gel electrophoresis and isolectric focusing. Both enzyme preparations were remarkably similar in physical and enzymic properties. Isoenzyme 1 had pI8.0 and a pH optimum of 9.0. The enzyme was active with pyruvate as amino acceptor but not with 2-oxoglutarate, and utilized various aromatic amino acids as amino donors in the following order of activity: phenylalanine greater than tyrosine greater than histidine. Very little activity was found with tryptophan and 5-hydroxytryptophan. The apparent Km values were about 2.6mM for histidine and 2.7 mM for phenylalanine. Km values for pyruvate were about 5.2mM with phenylalanine as amino donor and 1.1mM with histidine. The aminotransferase activity of the enzyme towards phenylalanine was inhibited by the addition of histidine. The mol.wt. determined by gel filtration and sucrose-density-gradient centrifugation was approx. 70000. The mitochondrial and supernatant isoenzyme 1 activities increased approximately 25-fold and 3.2-fold respectively in rats repeatedly injected with glucagon for 2 days. 2. An additional histidine-pyruvate aminotransferase (isoenzyme 2) was partially purified from both the mitochondrial and supernatant fractions of rat liver. Nearly identical properties were observed with both preparations. Isoenzyme 2 had pI5.2 and a pH optimum of 9.3. The enzyme was specific for pyruvate and did not function with 2-oxoglutarate. The order of effectiveness of amino donors was tyrosine = phenylalanine greater than histidine greater than tryptophan greater than 5-hydroxytryptophan. The apparent Km values for histidine and phenylalanine were about 0.51 and 1.8 mM respectively. Km values for pyruvate were about 3.5mM with phenylalanine and 4.7mM with histidine as amino donors. Histidine inhibited phenylalanine aminotransferase activity of the enzyme. Gel filtration and sucrose-density-gradient centrifugation yielded a mol.wt. of approx. 90000. Neither the mitochondrial nor the supernatant isoenzyme 2 activity was elevated by glucagon injection.

Animals↗
PubMed1976

Purification, characterization and identification of tryptophan aminotransferase from rat brain.

Tryptophan aminotransferase was purified from rat brain extracts. The purified enzyme had an isoelectric point at pH 6.2 and a pH optimum near 8.0. On electrophoresis the enzyme migrated to the anode. The enzyme was active with oxaloacetate or 2-oxoglutarate as amino acceptor but not with pyruvate, and utilized various L-amino acids as amino donors. With 2-oxoglutarate, the order of effectiveness of the L-amino acids was aspartate >> 5-hydroxytryptophan > tryptophan > tyrosine > phenylalanine. Aminotransferase activity of the enzyme towards tryptophan was inhibited by L-glutamate. Sucrose density gradient centrifugation gave a molecular weight of approx. 55,000. The enzyme was present in both the cytosol and synaptosomal cytosol, but not in the mitochondria. The isoelectric focusing profile of tryptophan: oxaloacetate aminotransferase activity was identical with that of L-aspartate: 2-oxoglutarate aminotransferase (EC 2.6.1.1) activity, with both subcellular fractions. On the basis of these data, it is suggested that the enzyme is identical with the cytosol aspartate: 2-oxoglutarate aminotransferase.

Animals↗
PubMed1976

Identity of kynurenine: pyruvate aminotransferase with histidine: pyruvate aminotransferase.

Kynurenine pyruvate aminotransferase was purified from rat kidney. The purified enzyme had an isoelectric point of pH 5.2 and a pH optimum of 9.3. The enzyme was active with pyruvate as amino acceptor but not with 2-oxoglutarate, and utilized various aromatic amino acids as amino donors. L-Amino acids were effective in the following order of activity: histidine greather than phenylalanine greater than kynurenine greater than tyrosine greater than tryptophan greater than 5-hydroxytryptophan. The apparent Km values were about 0.63 mM, 1.4 mM and 0.09 mM for histidine, kynurenine and phenylalanine, respectively. Km values for pyruvate were 5.5 mM with histidine as amino donor, 1.3 mM with kynurenine and 8.5 mM with phenylalanine. Kynurenine pyruvate aminotransferase activity of the enzyme was inhibited by the addition of histidine or phenylalanine. The molecular weights determined by gel filtration and sucrose density gradient centrifugation were approximately 76000 and 79000, respectively. On the basis of purification ratio, substrate specificity, inhibition by common substrates, subcellular distribution, isoelectric focusing and polyacrylamide-gel electrophoresis, it is suggested that kynurenine pyruvate aminotransferase is identical with histidine pyruvate aminotransferase and also with phenylalanine pyruvate aminotransferase. The physiological significance of the enzyme is discussed.

Animals↗
PubMed1975

Subcellular distribution and properties of kynurenine pyruvate transaminase in rat kidney.

Kynurenine transaminase activity in rat kidney was found in both the mitochondrial and supernatant fractions. These fractions contained (a) kynurenine pyruvate transaminase, which showed a preference for pyruvate as amino acceptor, and had a pH optimum between 8.0 and 8.5, and (b) kynurenine 2-oxoglutarate transaminase, with a preference for 2-oxoglutarate and a pH optimum between 6.0 and 6.5. The apparent Km value of the former enzyme for L-kynurenine was much lower than that of the latter enzyme.

Cytosol↗
PubMed1975

Subcellular distribution and properties of rat liver kynurenine transaminase.

Kynurenine transaminase activity in rat liver was found in both the mitochondrial and supernatant fractions. The mitochondrial and supernatant fractions contained (a) kynurenine pyruvate transaminase which showed a preference for pyruvate as amino-acceptor and a pH optimum between 8.0 and 8.5 and (b) kynurenine alpha-ketoglutarate transaminase with a preference for alpha-ketoglutarate and a pH optimum between 6.0 and 6.5.

Animals↗
PubMed1975

Kynurenine pyruvate transaminase and its specific inhibitor in rat intestine.

Kynurenine pyruvate transaminase was partially purified and characterized. The enzyme catalysed the conversion of L-knurenine to kynurenic acid. Transamination rates of 3-hydroxy-DL-kynurenine and 5-hydroxy-DL-kynurenine by the enzyme were 1/2.9 and 1/2.6 of kynurenine. The enzyme showed a higher preference for pyruvate than 2-oxoglutarate as aminoacceptor. The pH optimum of the reaction was 8.0 and 8.5. It was shown that the inhibitor of kynurenine pyruvate transaminase was present in the intestine.

Animals↗
PubMed1974

Subcellular distribution and properties of kynurenine transaminase in rat liver.

Kynurenine transaminase activity in rat liver was found in both the mitochondrial and supernatant fractions. The mitochondrial and supernatant fractions contained (a) kynurenine-pyruvate transaminase, which showed a preference for pyruvate as amino acceptor and a pH optimum between 8.0 and 8.5, and (b) kynurenine-alpha-oxoglutarate transaminase, with a preference for alpha-oxoglutarate and a pH optimum between 6.0 and 6.5. Possible roles of these enzymes in tryptophan metabolism in the liver are discussed.

Alcohol Oxidoreductases↗