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Biomedical subjects

T Noguchi

Publications and source records attributed to T Noguchi.

At least 1,081 records · Page 60Linked to original sources
PubMed1978

Peroxisomal localization of serine:pyruvate aminotransferase in human liver.

The distribution of L-serine:pyruvate aminotransferase (EC 2.6.1.51) in human liver was examined by centrifugation in a sucrose density gradient. The enzyme was located only in the peroxisomes and in the soluble fraction. The peroxisomal and soluble enzymes were highly purified and characterized. The two enzyme preparations had nearly identical properties, suggesting that the soluble enzyme is from broken peroxisomes. The two enzyme preparations showed different properties from rat liver serine:pyruvate aminotransferase (Noguchi, T., Okuno, E., and Kido, R. (1976) Biochem. J. 159, 607-613).

Cytosol↗
PubMed1978

Purification and properties of peroxisomal pyruvate (glyoxylate) aminotransferase from rat liver.

Pyruvate (glyoxylate) aminotransferase from rat liver peroxisomes was highly purified and characterized. The enzyme preparation has a mol.wt. of approx. 80,000 with two identical subunits, and isoelectric point of 8.0 and a pH optimum between 8.0 and 8.5. The enzyme catalysed transamination between a number of L-amino acids and pyruvate or glyoxylate. The effective amino acceptors were pyruvate, phenylpyruvate and glyoxylate with serine, and glyoxylate and phenylpyruvate with alanine as amino donor. These properties and kinetic parameters of the enzyme are remarkably similar to those previously described for mitochondrial alanine-glyoxylate aminotransferase isoenzyme 1 from glucagon-injected rat liver [Noguchi, Okuno, Takada, Minatogawa, Okai & Kido (1978, Biochem. J. 169, 113-122].

Alanine Transaminase↗
PubMed1978

Dibutyryl cyclic AMP increases the amount of functional messenger RNA coding for tyrosine aminotransferase in rat liver.

The administration of N6,O2-dibutyryl cyclic AMP and theophylline to adrenalectomized rats results in an increase in the amount of functional mRNA coding for tyrosine aminotransferase that can be isolated from liver. The induction of this specific mRNA, as quantitated in a mRNA-dependent reticulocyte lysate system, and using poly(A)+ mRNA extracted from total tissue and polysomes, is very rapid. Within an hour after the intraperitoneal injection of the cyclic AMP derivative there is a 5- to 7-fold elevation of functional mRNA coding for tyrosine aminotransferase (mRNATAT), and by 3 h this has returned to basal levels. In contrast, the 4- to 5-fold induction of tyrosine aminotransferase catalytic activity is maximal at 2 h and is still significantly greater than the basal level at 5 h. In the basal state, tyrosine aminotransferase mRNA codes for 0.019 +/- 0.003% of the protein synthesized in the in vitro system, whereas after cyclic nucleotide treatment this value 0.115 +/- 0.015%, hence the increase in mRNATAT activity is relatively specific. Cordycepin, at a concentration which prevents the accumulation in cytoplasm of poly(A)+ mRNA, completely blocks the increase in both the catalytic and mRNA activity of this enzyme. The marked increase in functional mRNA, the requirement for continued synthesis of poly(A)+ RNA, and the rapid induction and deinduction suggest that the cyclic nucleotide is enhancing specific mRNA synthesis and/or, processing, however an effect on mRNA degradation cannot be excluded.

Adrenalectomy↗
PubMed1978

Subcellular distribution of pyruvate (glyoxylate) aminotransferases in rat liver.

The distribution of pyruvate (glyoxylate) aminotransferases in the particulate fraction of rat liver homogenates was examined by centrifugation in a sucrose density graident. Aminotransferase activities towards serine, phenylalanine and histidine with pyruvate and those towards phenylalanine and histidine with glyoxylate were nearly identically distributed. Some 50-55% of the particulate activity was localized in the peroxisomes and the remainder in the mitochondria. Most of alanine-glyoxylate aminotransferase activity was localized in the mitochondria, with some activity in the peroxisomes. Glucagon injection resulted in increases of these enzyme activities in the mitochondria, but not in the peroxisomes.

Animals↗
PubMed1978

Characteristics of hepatic alanine-glyoxylate aminotransferase in different mammalian species.

Mitochondrial extracts of dog, cat, rat and mouse liver contain two forms of alanine-glyoxylate aminotransferase (EC 2.6.1.44): one, designated isoenzyme 1, has mol.wt. approx. 80 000 and predominates in dog and cat liver; the other, designated isoenzyme 2, has mol.wt. approx. 175 000 and predominates in rat and mouse liver. In rat and mouse liver, isoenzyme 1 activity was increased by the injection in vivo of glucagon, but not isoenzyme 2 activity. Isoenzyme 1 was purified and characterized from liver mitochondrial extracts of the four species. Both rat and mouse enzyme preparations catalysed transamination between a number of L-amino acids and glyoxylate, and with L-alanine as amino donor the effective amino acceptors were glyoxylate, phenylpyruvate and hydroxypyruvate. In contrast, both dog and cat enzyme preparations were specific for L-alanine and L-serine with glyoxylate, and used glyoxylate and hydroxypyruvate as effective amino acceptors with L-alanine. Evidence that isoenzyme 1 is identical with serine-pyruvate aminotransferase (EC 2.6.1.51) was obtained. Isoenzyme 2 was partially purified from mitochondrial extracts of rat and mouse liver. Both enzyme preparations were specific for L-alanine and glyoxylate. On the basis of physical properties and substrate specificity, it was concluded that isoenzyme 2 is a separate enzyme. Some other properties of isoenzymes 1 and 2 are described.

Alanine Transaminase↗
PubMed1978

[Biological activity of 1alpha-hydroxycholecalciferol (II). Effect on the metabolism of calcium and phosphorus in rats (author's transl)].

Effect of 1alpha-hydroxycholecalciferol on the metabolism of calcium and phosphorus was studied using Ca-labelled and non-labelled rats. With an oral daily dose of 2.5 or 12.5 microgram/kg of 1alpha-hydroxycholecalciferol, serum calcium, urine volume, urinary calcium excretion, urinary calcium concentration and water consumption increased, while fecal concentration, urinary phosphorus concentration and food consumption decreased. There was a lag time (1 or 2 days) between the increase of serum calcium and that of specific activity of serum calcium, and bone resorption was stimulated later than was intestinal calcium transport. After 10 days treatment, calcium concentration in the femur decreased, while a remarkable calcification was noted in soft tissues such as kidney, intestine, aorta, heart and muscle, although these effects were reduced with lower doses of the drug. With a smaller oral daily dose (0.1 or 0.5 microgram/kg), for 6 months, bone calcium and phosphorus concentration increased without soft tissue calcification. Thus, 1alpha-hydroxycholecalciferol may be an effective drug for patients with metabolic bone diseases.

Animals↗
PubMed1978

Purification and characterization of aromatic-amino-acid-glyoxylate aminotransferase from monkey and rat liver.

Aromatic-amino-acid-glyoxylate aminotransferase was highly purified from the mitochondrial fraction of livers from monkey and glucagon-injected rats. The two enzyme preparations showed physical and enzymic properties different from a kynurenine aminotransferase previously described. The two enzymes had nearly identical molecular weights (approximate 80 000), isoelectric points (pH 8.0) and pH optima (pH 8.0 - 8.5). However, a difference in substrate specificity was observed between the two enzymes. Both enzymes utilized glyoxylate, pyruvate, hydroxypyruvate and 2-oxo-4-methyl-thiobutyrate as effective amino acceptors. 2-Oxoglutarate was active for rat enzyme but not for monkey enzyme. With glyoxylate, amino donors were effective in the following order of activity; phenylalanine greater than histidine greater than tyrosine greater than tryptophan greater than 5-hydroxytrypotphan greater than kynurenine for the rat enzyme, and phenylalanine greater than kynurenine greater than histidine greater than tryptophan greater than 5-hydroxy-tryptophan for the monkey enzyme.

Amino Acids↗
PubMed1978

[Biological activity of 1alpha-hydroxycholecalciferol (1). Effect on intestine and bone in rats (author's transl)].

Biological activity of 1alpha-hydroxycholecalciferol was studied in rats. 1alpha-Hydroxycholecalciferol was found to be more potent and rapidly active than vitamin D in stimulating intestinal calcium transport and calcium mobilization from bone both in normal and vitamin D deficient rats. 1alpha-Hydroxycholecalciferol was also active in nephrectomized and/or thyroparathyroidectomized rats both in intestine and bone. Although it is well known that 1alpha-hydroxycholecalciferol is metabolized to 1alpha, 25-dihydroxycholecalciferol in the liver, there is the possibility that the former is active without further metabolism. In rats in which hepatitis was induced by CCl4, 1alpha-hydroxycholecalciferol was active both in the intestine and in the bone, while it was inactive in hepatectomized rats. These data clearly demonstrate that 1alpha-hydroxycholecalciferol is not active by itself and must be metabolized in the liver. This idea also shows the lag time in response of rats to 1alpha-hydroxycholecalciferol has more potent antirachitic activity than vitamin D and does not lose its activity with chronic oral administration. In view of these findings, 1alpha-hydroxycholecalciferol appears to have a good potential for clinical application in cases of renal failure and metabolic bone diseases.

Animals↗
PubMed1978

Suicide in Japan.

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Adolescent↗