Purification and properties of an NADP+-specific isocitrate dehydrogenase from Rhizobium meliloti.
An NADP+-specific isocitrate dehydrogenase has been purified and characterized from Rhizobium meliloti. The enzyme showed Mn++ or Mg++ requirement. The apparent Km values were 2.00 x 10(-5) M and 1.51 x 10(-5) M for DL-isocitrate and NADP+, respectively. The enzyme was inhibited by ATP, to a lesser extent by ADP and AMP. alpha-Ketoglutarate also inhibited the enzyme activity. Oxalacetate and glyoxylate together inhibited the enzyme activity. The inhibition was competitive. Studies with thiol inhibitors suggested that the enzyme contained a sulfhydryl group at or near the active site. The enzyme has an approximate molecular weight of 60,000. Fluorescence studies suggested that the enzyme contained tryptophan.
D000227:Adenine Nucleotides / Q000494:pharmacology; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D006038:Glyoxylates / Q000494:pharmacology; D007521:Isocitrate Dehydrogenase / Q000032:analysis / Q000302:isolation & purification*; D008970:Molecular Weight; D009249:NADP; D010071:Oxaloacetates / Q000494:pharmacology; D012231:Rhizobium / Q000201:enzymology*; D013050:Spectrometry, Fluorescence
D000227:Adenine Nucleotides; D006038:Glyoxylates; D010071:Oxaloacetates; D009249:NADP; D004228:Dithionitrobenzoic Acid; D007521:Isocitrate Dehydrogenase