title: Further insights into the isoenzyme composition and activity of glutamate dehydrogenase in Arabidopsis thaliana.
abstract: Following the discovery that in Arabidopsis, a third isoenzyme of NADH-dependent glutamate dehydrogenase (GDH) is expressed in the mitochondria of the root companion cells, we have re-examined the GDH isoenzyme composition. By analyzing the NADH-GDH isoenzyme composition of single, double and triple mutants deficient in the expression of the three genes encoding the enzyme, we have found that the α, β and γ polypeptides that comprise the enzyme can be assembled into a complex combination of heterohexamers in roots. Moreover, we observed that when one or two of the three root isoenzymes were missing from the mutants, the remaining isoenzymes compensated for this deficiency. The significance of such complexity is discussed in relation to the metabolic and signaling function of the NADH-GDH enzyme. Although it has been shown that a fourth gene encoding a NADPH-dependent enzyme is present in Arabidopsis, we were not able to detect corresponding enzyme activity, even in the triple mutant totally lacking NADH-GDH activity.
authors.affiliation: Equipe d'Accueil 3900; Biologie des Plantes et Innovation (BIOPI); Faculté de Pharmacie; Picardie, France.
authors.forename: Jean-Xavier
authors.initials: JX
authors.lastname: Fontaine
authors.forename: Thérèse
authors.initials: T
authors.lastname: Tercé-Laforgue
authors.forename: Sophie
authors.initials: S
authors.lastname: Bouton
authors.forename: Karine
authors.initials: K
authors.lastname: Pageau
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lea
authors.forename: Frédéric
authors.initials: F
authors.lastname: Dubois
authors.forename: Bertrand
authors.initials: B
authors.lastname: Hirel
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D017343:Genes, Plant; D005969:Glutamate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D007527:Isoenzymes; D008928:Mitochondria / Q000201:enzymology*; D009154:Mutation; D009243:NAD / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology*
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D010455:Peptides; D009243:NAD; D018698:Glutamic Acid; D005969:Glutamate Dehydrogenase
keywords: Arabidopsis; NADH-; NADPH-dependent activity; glutamate dehydrogenase; isoenzymes; roots