Regulation of lactate dehydrogenase activity in Actinomyces viscosus by adenosine-5′-triphosphate

Abstract

The lactate dehydrogenase (LDH) from Actinomyces viscosus strain T-6-1600 was inhibited by adenosine-5′-triphosphate (ATP). Enzyme activity was inhibited 100 per cent at ATP concentrations greater than 2 mM. The inhibition was specific for ATP since other mono-, di- and trinucleotides had little or no effect on the A. viscosus LDH. ATP appeared to exert its inhibitory effect through allosteric modulation of enzyme activity since kinetic data indicated that there are at least two ATP binding sites on the LDH from A. viscosus with some degree of cooperative interaction between them. The LDHs from a variety of A. viscosus strains studied showed this same type of allosteric interaction with ATP. Fructose-1,6-diphosphate (FDP), a positive effector for LDHs from several other microbial sources, had no effect on the enzyme from A. viscosus.