par Rasschaert, Joanne 
;Malaisse, Willy
Référence Biochemical medicine and metabolic biology, 48, 1, page (32-40)
Publication Publié, 1992
;Malaisse, Willy Référence Biochemical medicine and metabolic biology, 48, 1, page (32-40)
Publication Publié, 1992
Article révisé par les pairs
| Résumé : | D-Glucose causes a preferential stimulation of mitochondrial oxidative events relative to glycolysis in pancreatic islets. The possible participation of a Ca2+-induced activation of NAD-isocitrate dehydrogenase in this process was investigated. The activity of the enzyme in rat islet homogenates was measured through the generation of either NADH or 2- ketoglutarate. In the absence of Ca2+ and ADP, half-maximal velocities were recorded at isocitrate and NAD+ concentrations close to 1.2 and 0.5 mM, respectively. At isocitrate concentrations in the 0.15-1.5 mM range, ADP (1.0 mM) markedly increased the reaction velocity recorded in the absence of Ca2+ and conferred to the enzyme the property of being activated by Ca2+, with a K(d) for Ca2+ somewhat below 1.0 μM. From these data and by comparison with the activity of 2-ketoglutarate dehydrogenase, it is proposed that activation of NAD-isocitrate dehydrogenase by such factors as ADP and Ca2+ may be required in order to match, in nutrient-stimulated islets, the rates of 2-ketoglutarate generation and oxidative decarboxylation. |
