Effect of the urea-urease system and the carbonate ion on the activities of lactate dehydrogenase isoenzymes

Abstract

The inhibitory effect of urea on human and rabbit muscle M 4-lactate dehydrogenase ( l-lactate:NAD + oxidoreductase, EC 1.1.1.27) is markedly increased in the presence of urease. Evidence is presented suggesting that the action is due to the formation of CO 3 2− which under certain conditions may be shown to be a powerful inhibitor of the M 4 enzyme. NAD + protects the enzyme against both inhibitory systems. The H 4 enzyme, however, is relatively insensitive to both the urea-urease system and to CO 3 2−.