Evidence for an arginine residue at the coenzyme-binding site of Escherichia coli isocitrate dehydrogenase

• Published in: Biochemical journal Vol. 261; no. 1; pp. 301 - 304
• Main Authors: McKee, J S, Nimmo, H G
• Format: Journal Article
• Language: English
• Published: England 01.07.1989
• Subjects: arginine; Arginine - isolation & purification; Binding Sites; Coenzymes; Escherichia coli - enzymology; isocitrate dehydrogenase (NADP super(+)); Isocitrate Dehydrogenase - antagonists & inhibitors; Isocitrate Dehydrogenase - isolation & purification; NADP; Phenylglyoxal; Phosphorylation
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2610301

The arginine-specific reagent phenylglyoxal inactivated the active, dephosphorylated, form of Escherichia coli isocitrate dehydrogenase rapidly in a pseudo-first-order process. Both NADP+ and NADPH protected the enzyme against inactivation. Phenylglyoxal appeared to react with one arginine residue per subunit, and the extent of the reaction was proportional to the extent of the inactivation. In contrast, the phosphorylated form of isocitrate dehydrogenase did not react detectably with phenylglyoxal. The data indicate that the coenzyme-binding site of isocitrate dehydrogenase contains a reactive arginine residue that is protected by phosphorylation, and are consistent with the hypothesis that phosphorylation of the enzyme occurs close to or at its active site.