On the Regulation of a Bacterial Deoxycytidylate Deaminase

The presence of deoxycytidylate deaminase in extracts of Lactobacillus acidophilus has been confirmed. The partially purified enzyme is specifically stimulated by deoxycytidine triphosphate (Km = 1.7 x 10-7 m) and inhibited by deoxythymidine triphosphate (Ki = 1.7 x 10-6 m). Activation by the positive effector is probably mediated through a change in the interaction of the substrate (deoxycytidylate) with the enzyme, since deoxycytidine triphosphate influences the Michaelis constant, the Hill coefficient, and the shape of the substrate-saturation curve, but it has no effect on the maximal velocity of the reaction.