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Biomedical subjects

M Shin

Publications and source records attributed to M Shin.

At least 145 records · Page 8Linked to original sources
PubMed1983

Effect of dietary excess leucine on the levels of branched chain alpha-keto acids and ketone bodies in blood and the liver of rats.

Male rats were fed either a 10% casein diet or a 10% casein diet supplemented with 5% leucine, and the levels of alpha-ketoisocaproic acid and ketone bodies were analyzed in blood and the liver. alpha-Ketoisocaproic acid in plasma increased significantly on the 1st day of feeding the leucine-supplemented diet and was maintained on the high level during the experimental period of 7 days. Other branched chain alpha-keto acids tended to decrease in plasma. beta-Hydroxybutyric acid in blood doubled its amount on the 1st day on the high leucine diet and was maintained high during the experimental period. The sum of acetoacetic acid and beta-hydroxybutyric acid in blood was kept on a level twice as high as that of the control group. Ketone bodies in the liver were similarly increased and the sum of acetoacetic acid and beta-hydroxybutyric acid in the liver corresponded to the level found inhibitory to NAD biosynthesis in in vitro system [YAMADA, O., et al.: Int. J. Vit. Nutr. Res. 53, 184 (1983)].

Animals↗
PubMed1982

Immobilized ferredoxin-NADP+ reductase: preparation and properties.

Immobilized ferredoxin-NADP+ reductase (FNR) was prepared by coupling reaction of CNBr-Sepharose 4B with the spinach enzyme. The immobilized FNR was found to retain the activity of complex formation with ferredoxin as well as the enzymatic activities such as NADPH-diaphorase and NADPH-cytochrome c reductase activities. The complex formation of immobilized FNR with ferredoxin was investigated by measuring reflex spectra of the immobilized FNR with or without ferredoxin and by titration with ferredoxin. The experimental results obtained for the dissociation constant, pH profile and effect of salts were coincidental with those reported for the free enzyme system.

Enzymes, Immobilized↗
PubMed1982

Effect of L-tryptophan and L-leucine on biosynthesis of niacin-related compounds in Saccharomyces carlsbergensis.

As a model system for investigating the mechanism of the hepatic NAD-lowering effect of leucine in rats, aerobically grown Saccharomyces carlsbergensis was used in this paper. Tryptophan supplementation of the medium doubled total niacin production by S. carlsbergensis. This elevation in total niacin was mainly due to increases in niacin (14 times) and niacinamide nucleotides (2 times). Among nucleotides, the NAD level doubled whereas NADH, NADP and NADPH levels dropped significantly. Simultaneous supplementation of the medium with leucine suppressed the elevation in total and free niacin levels. In the presence of tryptophan, approximately 50% of the total niacin was secreted in the medium in the form of free niacin, while in the presence of both tryptophan and leucine most of the total niacin remained in the cell. The specific activity of quinolinate phosphoribosyltransferase [EC 2.4.2.19] was not affected by supplementation of the medium with tryptophan and/or leucine. In contrast, the specific activity of nicotinamide deamidase [EC 3.5.1.19] increased fivefold in the presence of tryptophan. Simultaneous supplementation of the medium with leucine tryptophan. Simultaneous supplementation of the medium with leucine suppressed the increase in nicotinamide deamidase. Cellular incorporation of tryptophan was not affected by leucine simultaneously added as a supplement to the medium. Leucine did not have any inhibitory effect on total niacin synthesis from 3-hydroxyanthranilate. From the results, a possible mechanism for the inhibitory effect of leucine on the tryptophan-NAD pathway was discussed.

Culture Media↗
PubMed1982

Inhibition of L-kynurenine 3-hydroxylase from Saccharomyces carlsbergensis by alpha-keto acid derivatives of branched chain amino acids.

L-Kynurenine 3-hydroxylase [EC 1.14.1.2] was partially purified from the mitochondrial outer membrane fraction of Saccharomyces carlsbergensis by Sephadex G-200 gel chromatography, and the effects of leucine and its related compounds on the enzyme were investigate. Alpha-Keto acid derivatives of the the three branched chain amino acids were found inhibitory to the partially purified kynurenine 3-hydroxylase, but branched chain amino acids were without effect. Alpha-Ketoisocaproate (KIC), a keto acid analogue of L-leucine, inhibited kynurenine 3-hydroxylase noncompetitively with apparent Ki values of 4.2 and 8.3 mM for kynurenine and NADPH respectively. Alpha-Ketoglutarate and pyruvate were mixed-type inhibitors of the enzyme. KIC production by S. carlsbergensis grown in medium containing no leucine was negligible, while that in leucine incorporated into cells. From the results, it was proposed that KIC produced from leucine lowered synthesis of NAD from tryptophan by inhibiting L-kynurenine 3-hydroxylase, a possible rate-limiting enzyme in the tryptophan-NAD pathway in Saccharomyces carlsbergensis.

Amino Acids, Branched-Chain↗
PubMed1982

Effect of branched chain alpha-keto acids on kynurenine 3-hydroxylase from rat liver.

In the preceding paper, we found that branched chain alpha-keto acids, alpha-ketoglutarate and pyruvate were inhibitory to kynurenine 3-hydroxylase [EC 1.14.1.2] from Saccharomyces (Shin, M. et al. (1982): J. Nutr. Sci. vitaminol., 28, 191-201). As kynurenine 3-hydroxylase is reported to be a rate-limiting enzyme in the tryptophan-NAD pathway in rats, branched chain amino acids, branched chain alpha-keto acids and several other keto acids were tested for their effects on kynurenine 3-hydroxylase activity in the mitochondrial outer membrane fraction prepared from rat liver. In contrast with the yeast enzyme, the rat liver enzyme was resistant to alpha-keto acid-inhibition and more than 70% of the enzyme activity was maintained even in the presence of 20 mM of each alpha-keto acid. The present result implies that the mechanism of the hepatic NAD-lowering effect of leucine in rats might be completely different from that operative in Saccharomyces.

Amino Acids, Branched-Chain↗
PubMed1982

NAD glycohydrolase activity in the liver of rats fed on excess leucine diet and low or high protein diet.

In rats fed for 2 weeks on a 10% casein diet supplemented with 5% leucine, the hepatic NAD content was lowered when comparing with the control rats pair-fed on the 10% casein diet. The hepatic NAD glycohydrolase [EC 3.2.2.5] activity increased by 25% in the leucine-supplemented diet-fed rats and by 40% in the nicotinic acid-free diet-fed rats. The hepatic NAD glycohydrolase activity in the rats fed on the nonprotein diet freely for 1 week was elevated by 60% compared to the rats fed on the 18% casein diet. The hepatic NAD content in the former animals was significantly lower than that in the latter. The 70% casein diet caused changes in neither hepatic NAD content nor NAD glycohydrolase activity. These results indicated an inverse relationship between hepatic NAD content and NAD glycohydrolase activity.

Animals↗
PubMed1979

Properties of common wheat ferredoxin, and a comparison with ferredoxins from related species of triticum and aegilops.

Wheat ferredoxin was purified from the leaves of common wheat (Triticum aestivum). The absorption spectrum showed maxima at 465, 425, 332, and 278 nm. The absorbance ratio, A425 nm/A278 nm was 0.49, and the millimolar extinction coefficient at 425 nm was 10.8 mM-1. cm-1. The amino acid composition was determined to be Lys5, His2, Arg1, Asp11, Thr5, Ser7, Glu18, Pro5, Gly6, Ala7, Cys5, Val7, Met1, Ile4, Leu7, Tyr4, Phe1, and Trp1. The total number of amino acid residues was 97. The molecular weight was calculated from the amino acid composition to be 10,829, including iron and sulfur atoms. This value was confirmed by other methods, which were based on the contents of non-heme iron and of terminal amino acid. The N-terminal amino acid was alanine, and the C-terminal amino acid sequence was -Glu-Leu-Thr-AlaCOOH. Comparative studies were performed between T. aestivum ferredoxin and ferredoxins isolated from closely related species; these were T. aegilopoides, T. durum, Ae. squarrosa, and Ae. ovata. No significant differences in the properties of these ferredoxins were detected. It was also shown that these ferredoxins are immunologically homologous. It is, therefore, likely that one molecular species of ferredoxin is distributed through two genera of Triticum and Aegilops.

Amino Acids↗
PubMed1979

Effect of dietary excess leucine on nicotinamide nucleotide level in rat liver.

1. Six groups of rats were freely fed diets containing casein at 5, 10 and 20% levels with and without nicotinic acid. After 2 weeks on these diets, hepatic nicotinamide nucleotide and free nicotinic acid concentrations were studied. 2. Hepatic nicotinamide nucleotide level was kept in the normal range in rats fed the 10 and 20% casein diets with and without nicotinic acid. 3. L-leucine supplemented at the 5% level to the 10 and 20% casein diets caused significant decrease in hepatic nicotinamide nucleotide level only in rats fed nicotinic acid devoid diet. 4. Hepatic nicotinamide nucleotide in rats fed the diet in which casein was replaced by zein increased significantly by adding nicotinic acid. This increase in the hepatic nicotinamide nucleotide caused by dietary supplemented nicotinic acid was not reduced by the addition of L-leucine. 5. The hepatic free nicotinic acid level did not change even in rats of which hepatic nicotinamide nucleotide was significantly reduced. 6. Urinary excretion of nicotinic acid and N-methylnicotinamide was increased significantly by adding nicotinic acid to the diet but was not affected by adding L-leucine at the 5% level. 7. From the above results, a possible mechanism of L-leucine action was discussed.

Administration, Oral↗
PubMed1978

Ferredoxin-Sepharose 4B as a tool for the purification of ferredoxin-NADP+ reductase.

Ferredoxin immobilized on Sepharose 4B was prepared by reaction of CNBr-Sepharose 4B with spinach ferredoxin. The ferredoxin-Sepharose 4B conjugated ferredoxin-NADP+ reductase (NADPH: ferredoxin oxidoreductase, [EC 1.6.7.1]) in dilute buffer solution and released it in high salt concentrations. A novel method of preparation for the reductase was established by a combination of affinity adsorption on the ferredoxin-Sepharose 4B column with usual purification procedures. It was found using the new method, that there are two forms of ferredoxin-NADP+ reductase, FNR I and FNR II, in spinach. Comparative studies of the two components suggest that FNR I may be a dimer of FNR II.

Chromatography, Affinity↗
PubMed1977

Two plant-type ferredoxins from a blue-green alga, Nostoc verrucosum.

Two plant-type ferredoxins were isolated and purified from a blue-green alga, Nostoc verrucosum. They were separable by chromatography on a DEAE-cellulose column. The slow-moving band was designated ferredoxin I (Fd I) and the fast-moving band was ferredoxin II (Fd II). The ratio of the yield of ferredoxins I and II was about 1 : 0.84. Both ferredoxins had absorption spectra similar to those of plant-type ferredoxins. Two atoms of non-heme iron and two of labile sulfur were found per mol of both ferredoxin I and ferredoxin II. Their molecular weights were identical and estimated to be about 18 000 by a gel filtration method. The biochemical activities of these Nostoc ferredoxins were studied: the NADP photoreduction activity on one hand and the NADP-cytochrome c reductase activity on the other.

Chloroplasts↗
PubMed1976

Metastatic teratocarcinoma following chemotherapy. Maturation to a mass pathologically indistinguishable from a mediastinal enteric cyst.

A case of testicular teratocarcinoma metastatic to a mediastinal lymph node and associated with a mediastinal lesion indistinguishable from an enteric cyst is presented. It is postulated that the mediastinal enteric cyst-like lesion resulted from histologic maturation of metastatic teratocarcinoma after intensive chemotherapy. The basis in the medical literature for this postulate is detailed.

Adult↗