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Identification of six novel allosteric effectors of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase isoforms. Physiological context sets the specificity Inra
Curien, G.; Ravanel, S.; Robert, M.; Dumas, R..
The Arabidopsis genome contains two genes predicted to code for bifunctional aspartate kinase-homoserine dehydrogenase enzymes (isoforms I and II). These two activities catalyze the first and the third steps toward the synthesis of the essential amino acids threonine, isoleucine, and methionine. We first characterized the kinetic and regulatory properties of the recombinant enzymes, showing that they mainly differ with respect to the inhibition of the homoserine dehydrogenase activity by threonine. A systematic search for other allosteric effectors allowed us to identify an additional inhibitor (leucine) and 5 activators (alanine, cysteine, isoleucine, serine, and valine) equally efficient on aspartate kinase I activity (4-fold activation). The six...
Tipo: Journal Article Palavras-chave: VOIE METABOLIQUE; ACIDE AMINE ESSENTIEL; ASPARTATE KINASE HOMOSERINE DEHYDROGENASE; ISOFORME; EFFECTEUR ALLOSTERIQUE; INHIBITION ENZYMATIQUE; THREONINE; ISOLEUCINE; METHIONINE; ACTIVITE ENZYMATIQUE.
Ano: 2005 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB9500032200111312&uri=/notices/prodinra1/2010/11/
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Mechanism of control of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase by threonine Inra
Paris, S.; Viemon, C.; Curien, G.; Dumas, R..
The regulatory domain of the bifunctional threonine-sensitive aspartate kinase homoserine dehydrogenase contains two homologous subdomains defined by a common loop-αhelix-loop-β strand-loop-β strand motif. This motif is homologous with that found in the two subdomains of the biosynthetic threonine-deaminase regulatory domain. Comparisons of the primary and secondary structures of the two enzymes allowed us to predict the location and identity of the amino acid residues potentially involved in two threonine-binding sites ofArabidopsis thaliana aspartate kinase-homoserine dehydrogenase. These amino acids were then mutated and activity measurements were carried out to test this hypothesis. Steady-state kinetic experiments on the wild-type and mutant enzymes...
Tipo: Journal Article Palavras-chave: ASPARTOKINASE; GENE THRA; DESAMINASE; STRUCTURE ENZYMATIQUE; INHIBITION ENZYMATIQUE; SEQUENCE NUCLEOTIDIQUE; THREONINE.
Ano: 2003 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0400031090101858&uri=/notices/prodinra1/2010/11/
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Methionine metabolism in plants. Chloroplasts are autonomous for de novo methionine synthesis and can import s-adenosylmethionine from the cytosol Inra
Ravanel, S.; Block, M.A.; Rippert, P.; Jabrin, S.; Curien, G.; Rébeillé, F.; Douce, R..
The subcellular distribution of Met and S-adenosylmethionine (AdoMet) metabolism in plant cells discloses a complex partition between the cytosol and the organelles. In the present work we show that Arabidopsis contains three functional isoforms of vitamin B12-independent methionine synthase (MS), the enzyme that catalyzes the methylation of homocysteine to Met with 5-methyltetrahydrofolate as methyl group donor. One MS isoform is present in chloroplasts and is most likely required to methylate homocysteine that is synthesized de novo in this compartment. Thus, chloroplasts are autonomous and are the unique site for de novo Met synthesis in plant cells. The additional MS isoforms are present in the cytosol and are most probably involved in the regeneration...
Tipo: Journal Article Palavras-chave: ARABIDOPSIS THALIANA; PHYSIOLOGIE CELLULAIRE; METHIONINE-SYNTHASE; S-ADENOSYLMETHIONINE; LOCALISATION CELLULAIRE; METHIONINE; CHLOROPLASTE.
Ano: 2004 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0400031395104830&uri=/notices/prodinra1/2010/11/
Registros recuperados: 3
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