Identification of essential arginyl residues in cytoplasmic malate dehydrogenase with butanedione.

摘要: The inactivation of cytoplasmic malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37) from porcine heart and the specific modification arginyl residues have been found to occur when enzyme is inhibited with reagent butanedione in sodium borate buffer. was follow pseudo-first order kinetics. This loss enzymatic activity concomitant 4 per molecule enzyme. All could be made inaccessible a dehydrogenase-NADH-hydroxymalonate ternary complex formed. Only 2 were protected by NADH alone appear essential. Studies phosphate buffer reactivation activity, upon removal excess borate, support role ion stabilization mechanism previously reported Riordan (Riordan, J.F. (1970) Fed. Proc. 29, Abstr. 462; Riordan, (1973) Biochemistry 12, 3915-3923). Protection also provided competitive inhibitor AMP, while nicotinamide exhibited no effect. Such results suggest that AMP moiety major importance ability protect When fluorescence titrations used monitor form binary hydroxymalonate, only formation seemed effected arginine modification.