Comparison of the effects of Ca2+, adenine nucleotides and pH on the kinetic properties of mitochondrial NAD(+)-isocitrate dehydrogenase and oxoglutarate dehydrogenase from the yeast Saccharomyces cerevisiae and rat heart

• Published in: Biochemical journal 1994-10, Vol.303 ( Pt 2) (2), p.461-465
• Main Authors: Nichols, B J, Rigoulet, M, Denton, R M
• Format: Article
• Language: English
• Subjects: Adenine Nucleotides - pharmacology; Adenosine Diphosphate - pharmacology; Adenosine Monophosphate - pharmacology; Adenosine Triphosphate - pharmacology; Amino Acid Sequence; Animals; Calcium - pharmacology; Consensus Sequence; Hydrogen-Ion Concentration; Isocitrate Dehydrogenase - chemistry; Isocitrate Dehydrogenase - drug effects; Isocitrate Dehydrogenase - metabolism; Ketoglutarate Dehydrogenase Complex - drug effects; Ketoglutarate Dehydrogenase Complex - metabolism; Ketoglutaric Acids - pharmacology; Kinetics; Male; Mitochondria, Heart - enzymology; Molecular Sequence Data; Rats; Saccharomyces cerevisiae - enzymology
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3030461

The regulatory properties of NAD(+)-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of yeast and rat heart mitochondria were studied under identical conditions. Yeast NAD(+)-isocitrate dehydrogenase exhibits a low K0.5 for isocitrate and is activated by AMP and ADP, but is insensitive to ATP and Ca2+. In contrast, the rat heart NAD(+)-isocitrate dehydrogenase was insensitive to AMP, but was activated by ADP and by Ca2+ in the presence of ADP or ATP. Both yeast and rat heart oxoglutarate dehydrogenase were stimulated by ADP, but only the heart enzyme was activated by Ca2+. All the enzymes studied were activated by decreases in pH, but to differing extents. The effects of Ca2+, adenine nucleotides and pH were through K0.5 for isocitrate or 2-oxoglutarate. These observations are discussed with reference to the deduced amino acid sequences of the constituent subunits of the enzymes, where they are available.