A reactive arginine in adenylate kinase.

Adenylate kinase (ATP:AMP phosphotransferase, EV 2.7.4.3) from pig heart is inactivated by the specific arginyl reagent phenylglyoxal. During inactivation two molecules of phenyglyoxal are incorporated into the protein indicating the modification of one of the 11 arginine residues. The modification of other amino acids is ruled out. Chemical modification of this essential residue is prevented by high concentrations of the substrates AMP, ADP and MgATP2-. The protection of the substrates is explained by the formation of a ternary abortive enzyme-substrate complex ESS. The dissociation constants KD = [ES] - [S]/[ESS] are determined from the kinetic data of inactivation and protection.