title: Malate dehydrogenase, inhibition of pig heart supernatant enzyme by iodoacetamide.
abstract: Pig heart supernatant malate dehydrogenase is alkylated by 250 mM iodoacetamide at 37 degrees C in pH 7.5 Tris/acetate buffer which is 0.05 M with respect to acetate to form enzyme with 1,3-dicarboxamidomethyl histidine, 3-carboxamidomethyl histidine, 1-carboxamidomethyl histidine, carboxamidomethyl cysteine, and carboxamidomethyl methionine. 1,3-Dicarboxamidomethyl histidine forms with a stoichiometry of 1/enzyme subunit at a rate equaling the rate (approximately 1.24 +/- 0.09 X 10(-2) min-1) of enzyme inactivation by iodoacetamide. All other amino acid derivatives form at a slower rate initially or continuously. The enzyme is protected against inactivation by iodoacetamide through NADH binding, suggesting that there is an "essential" histidine residue at or near the active site.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000201:enzymology; D007460:Iodoacetamide / Q000494:pharmacology*; D007461:Iodoacetates / Q000494:pharmacology*; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors*; D009206:Myocardium / Q000201:enzymology*; D013552:Swine
chemical_list: D007461:Iodoacetates; D008291:Malate Dehydrogenase; D007460:Iodoacetamide