The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Nanaya Tamaki - One of the best experts on this subject based on the ideXlab platform.
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Identity of D-3-aminoisobutyrate-pyruvate aminotransferase with alanine-Glyoxylate aminotransferase 2
Biochimica et biophysica acta, 1993Co-Authors: Yasuhide Kontani, Masae Kaneko, Mariko Kikugawa, Shigeko Fujimoto, Nanaya TamakiAbstract:D-3-Aminoisobutyrate-pyruvate aminotransferase (EC 2.6.1.40) and alanine-Glyoxylate aminotransferase 2 (EC 2.6.1.44) were co-purified from rat liver as a single protein. The ratio of the two activities remained constant after Sephacryl S-200 chromatography and chromatofocussing. The Km value for beta-alanine as a substrate with 1 mM glyloxylate as amino group acceptor was 1.4 mM. The activity was inhibited by (S)-alanine with Ki = 2.2 mM. The Km for (S)-alanine as substrate with 1 mM Glyoxylate as amino group was 6 mM. This activity was inhibited competitively by beta-alanine with Ki = 0.7 mM. (R)-3-aminoisobutyric acid, 5-aminolevulinic acid, NG,NG'-dimethyl-(S)-arginine, and (S)-2-aminobutyric acid were active competitively with respect to beta-alanine with Km of 0.12 mM, 2.1 mM, 6.4 mM and 11.3 mM, respectively. Antiserum to rat liver D-3-aminoisobutyrate-pyruvate aminotransferase inhibited alanine-Glyoxylate aminotransferase activity in rat liver in the same way as that of D-3-aminoisobutyrate-pyruvate aminotransferase. Alanine-Glyoxylate aminotransferase activity and D-3-aminoisobutyrate-pyruvate aminotransferase activities were inactivated competitively with respect to beta-alanine by 5-fluorouracil and 6-azauracil, which are chemotherapeutic reagents used to cancer. These experiments indicate that D-3-aminoisobutyrate-pyruvate aminotransferase is identical with alanine-Glyoxylate aminotransferase 2, aminolevulinate aminotransferase, 2-aminobutyrate aminotransferase and dimetylarginine-pyruvate aminotransferase.
Leszek A. Kleczkowski - One of the best experts on this subject based on the ideXlab platform.
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The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants
Plant physiology, 1992Co-Authors: Curtis V. Givan, Leszek A. KleczkowskiAbstract:Glyoxylate and hydroxypyruvate are metabolites involved in the pathway of carbon in photorespiration. The chief Glyoxylate-reducing enzyme in leaves is now known to be a cytosolic Glyoxylate reductase that uses NADPH as the preferred cofactor but can also use NADH. Glyoxylate reductase has been isolated from spinach leaves, purified to homogeneity, and characterized kinetically and structurally. Chloroplasts contain lower levels of Glyoxylate reductase activity supported by both NADPH and NADH, but it is not yet known whether a single chloroplastic enzyme catalyzes Glyoxylate reduction with both cofactors. The major hydroxypyruvate reductase activity of leaves has long been known to be a highly active enzyme located in peroxisomes; it uses NADH as the preferred cofactor. To a lesser extent, NADPH can also be used by the peroxisomal enzyme. A second hydroxypyruvate reductase enzyme is located in the cytosol; it preferentially uses NADPH but can also use NADH as cofactor. In a barley mutant deficient in peroxisomal hydroxypyruvate reductase, the NADPH-preferring cytosolic form of the enzyme permits sufficient rates of hydroxypyruvate reduction to support continued substrate flow through the terminal stages of the photosynthetic carbon oxidation (glycolate/glycerate) pathway. The properties and metabolic significance of the cytosolic and organelle-localized Glyoxylate and hydroxypyruvate reductase enzymes are discussed.
Jens Nielsen - One of the best experts on this subject based on the ideXlab platform.
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Biosynthesis of Glyoxylate from glycine in Saccharomyces cerevisiae.
FEMS yeast research, 2005Co-Authors: Silas G. Villas-boas, Mats Åkesson, Jens NielsenAbstract:Glyoxylate biosynthesis in Saccharomyces cerevisiae is traditionally mainly ascribed to the reaction catalyzed by isocitrate lyase (Icl), which converts isocitrate to Glyoxylate and succinate. However, Icl is generally reported to be repressed by glucose and yet Glyoxylate is detected at high levels in S. cerevisiae extracts during cultivation on glucose. In bacteria there is an alternative pathway for Glyoxylate biosynthesis that involves a direct oxidation of glycine. Therefore, we investigated the glycine metabolism in S. cerevisiae coupling metabolomics data and 13C-isotope-labeling analysis of two reference strains and a mutant with a deletion in a gene encoding an alanine:Glyoxylate aminotransferase. The strains were cultivated on minimal medium containing glucose or galactose, and 13C-glycine as sole nitrogen source. Glyoxylate presented 13C-labeling in all cultivation conditions. Furthermore, Glyoxylate seemed to be converted to 2-oxovalerate, an unusual metabolite in S. cerevisiae. 2-Oxovalerate can possibly be converted to 2-oxoisovalerate, a key precursor in the biosynthesis of branched-chain amino acids. Hence, we propose a new pathway for glycine catabolism and Glyoxylate biosynthesis in S. cerevisiae that seems not to be repressed by glucose and is active under both aerobic and anaerobic conditions. This work demonstrates the great potential of coupling metabolomics data and isotope-labeling analysis for pathway reconstructions.
Yasuhide Kontani - One of the best experts on this subject based on the ideXlab platform.
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Identity of D-3-aminoisobutyrate-pyruvate aminotransferase with alanine-Glyoxylate aminotransferase 2
Biochimica et biophysica acta, 1993Co-Authors: Yasuhide Kontani, Masae Kaneko, Mariko Kikugawa, Shigeko Fujimoto, Nanaya TamakiAbstract:D-3-Aminoisobutyrate-pyruvate aminotransferase (EC 2.6.1.40) and alanine-Glyoxylate aminotransferase 2 (EC 2.6.1.44) were co-purified from rat liver as a single protein. The ratio of the two activities remained constant after Sephacryl S-200 chromatography and chromatofocussing. The Km value for beta-alanine as a substrate with 1 mM glyloxylate as amino group acceptor was 1.4 mM. The activity was inhibited by (S)-alanine with Ki = 2.2 mM. The Km for (S)-alanine as substrate with 1 mM Glyoxylate as amino group was 6 mM. This activity was inhibited competitively by beta-alanine with Ki = 0.7 mM. (R)-3-aminoisobutyric acid, 5-aminolevulinic acid, NG,NG'-dimethyl-(S)-arginine, and (S)-2-aminobutyric acid were active competitively with respect to beta-alanine with Km of 0.12 mM, 2.1 mM, 6.4 mM and 11.3 mM, respectively. Antiserum to rat liver D-3-aminoisobutyrate-pyruvate aminotransferase inhibited alanine-Glyoxylate aminotransferase activity in rat liver in the same way as that of D-3-aminoisobutyrate-pyruvate aminotransferase. Alanine-Glyoxylate aminotransferase activity and D-3-aminoisobutyrate-pyruvate aminotransferase activities were inactivated competitively with respect to beta-alanine by 5-fluorouracil and 6-azauracil, which are chemotherapeutic reagents used to cancer. These experiments indicate that D-3-aminoisobutyrate-pyruvate aminotransferase is identical with alanine-Glyoxylate aminotransferase 2, aminolevulinate aminotransferase, 2-aminobutyrate aminotransferase and dimetylarginine-pyruvate aminotransferase.
Curtis V. Givan - One of the best experts on this subject based on the ideXlab platform.
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The Enzymic Reduction of Glyoxylate and Hydroxypyruvate in Leaves of Higher Plants
Plant physiology, 1992Co-Authors: Curtis V. Givan, Leszek A. KleczkowskiAbstract:Glyoxylate and hydroxypyruvate are metabolites involved in the pathway of carbon in photorespiration. The chief Glyoxylate-reducing enzyme in leaves is now known to be a cytosolic Glyoxylate reductase that uses NADPH as the preferred cofactor but can also use NADH. Glyoxylate reductase has been isolated from spinach leaves, purified to homogeneity, and characterized kinetically and structurally. Chloroplasts contain lower levels of Glyoxylate reductase activity supported by both NADPH and NADH, but it is not yet known whether a single chloroplastic enzyme catalyzes Glyoxylate reduction with both cofactors. The major hydroxypyruvate reductase activity of leaves has long been known to be a highly active enzyme located in peroxisomes; it uses NADH as the preferred cofactor. To a lesser extent, NADPH can also be used by the peroxisomal enzyme. A second hydroxypyruvate reductase enzyme is located in the cytosol; it preferentially uses NADPH but can also use NADH as cofactor. In a barley mutant deficient in peroxisomal hydroxypyruvate reductase, the NADPH-preferring cytosolic form of the enzyme permits sufficient rates of hydroxypyruvate reduction to support continued substrate flow through the terminal stages of the photosynthetic carbon oxidation (glycolate/glycerate) pathway. The properties and metabolic significance of the cytosolic and organelle-localized Glyoxylate and hydroxypyruvate reductase enzymes are discussed.