title: Physiological regulation of isocitrate dehydrogenase and the role of 2-oxoglutarate in Prochlorococcus sp. strain PCC 9511.
abstract: The enzyme isocitrate dehydrogenase (ICDH; EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate, to produce 2-oxoglutarate. The incompleteness of the tricarboxylic acids cycle in marine cyanobacteria confers a special importance to isocitrate dehydrogenase in the C/N balance, since 2-oxoglutarate can only be metabolized through the glutamine synthetase/glutamate synthase pathway. The physiological regulation of isocitrate dehydrogenase was studied in cultures of Prochlorococcus sp. strain PCC 9511, by measuring enzyme activity and concentration using the NADPH production assay and Western blotting, respectively. The enzyme activity showed little changes under nitrogen or phosphorus starvation, or upon addition of the inhibitors DCMU, DBMIB and MSX. Azaserine, an inhibitor of glutamate synthase, induced clear increases in the isocitrate dehydrogenase activity and icd gene expression after 24 h, and also in the 2-oxoglutarate concentration. Iron starvation had the most significant effect, inducing a complete loss of isocitrate dehydrogenase activity, possibly mediated by a process of oxidative inactivation, while its concentration was unaffected. Our results suggest that isocitrate dehydrogenase responds to changes in the intracellular concentration of 2-oxoglutarate and to the redox status of the cells in Prochlorococcus.
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: María Agustina
authors: MA
authors: Domínguez-Martín
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: Antonio
authors: A
authors: López-Lozano
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: Jesús
authors: J
authors: Diez
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: Guadalupe
authors: G
authors: Gómez-Baena
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: Oriol Alberto
authors: OA
authors: Rangel-Zúñiga
authors: Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Córdoba, Spain.
authors: José Manuel
authors: JM
authors: García-Fernández
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D007521:Isocitrate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D007656:Ketoglutaric Acids / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D048929:Prochlorococcus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D009249:NADP; D007521:Isocitrate Dehydrogenase