Some properties of creatine phosphokinase

Abstract

The enzyme creatine phosphokinase requires SH groups for its activity, but has no obligatory requirement for added cysteine. The enzyme has a well-defined opt. pH = 7.2 and 10.5 for catalyzing the forward and reverse reactions, respectively, as expressed in the equation, phosphocreatine + ADPATP + creatine. The presence of Ca++ or Mg++ is obligatory, but the absolute amounts required depend on the nature of the reaction. (i.e. forward or reverse). Excess amts. of Ca++ or Mg++ are inhibitory in the case of the forward reaction and alter the equilibrium in the case of the reverse reaction. AMP could not serve as a phosphate acceptor. p-Chloromercuribenzoate, N-ethylmaleimide, iodoacetate, dinitro-o-cresol, phosphate, citrate, fluoride and ethylene-diaminetetraacetic acid were inhibitory.