Adenylate kinase inhibition by adenosine 5'-monophosphate and fluoride in the determination of creatine kinase activity.

The current methods for the determination of creatine kinase (EC 2.7.3.2) activity are derived from Oliver's method, in which AMP is used to decrease interference by adenylate kinase (EC 2.7.4.3). Recently, Szasz et al. and Rosano et al. described methods in which diadenosine pentaphosphate and fluoride, respectively, are used to reduce this interference. However, diadenosine pentaphosphate does not sufficiently inhibit such activity of hepatic origin, while fluoride alone can only inhibit it at concentrations at which the fluoride tends to precipitate as MgF2. Finally, Szasz et al., the Committee on Enzymes of the Scandinavian Society for Clinical Chemistry and Clinical Physiology, and the German Society for Clinical Chemistry have proposed methods in which both AMP and diadenosine pentaphosphate are used to inhibit adenylate kinase. We have found that by using low concentrations of AMP and fluoride together, we can greatly diminish this interference without significant loss of creatine kinase activity and with no precipitation of MgF2.