Selective chemical modification of arginine residues in mitochondrial malate dehydrogenase

Mitochondrial malate dehydrogenase (L-malate: NAD⁺ oxidoreductase, EC 1.1.1.37) from porcine heart exhibits a time dependent loss in enzymatic activity in the presence of the reagent butanedione. The inhibition occurs concomitant with the modification of 2.4 residues of arginine per molecular weight of 70,000. The presence of the reduced coenzyme, NADH, protects the enzyme from inhibition by butanedione and from modification of arginine residues, suggesting that the residues modified are located near the coenzyme binding site and hence at or near the enzymatic active center of this enzyme.