ABSTRACT
This chapter discusses two cases applicable to unireactant cases: where there is an exclusive or obligatory interaction of the free metal with the free enzyme and where there is an exclusive interaction of the free metal with the free substrate and not the free enzyme. Many of those unireactant cases which involve nucleotide substrates usually require what appears to be a simultaneous participation of a divalent metal ion in stoichiometric concentrations. The probable mechanism for the activation is the obligatory binding of the cation with the substrate prior to its interaction with the enzyme. Creatine kinase has proved to be an excellent model for the study of the effect of metal cofactors. With a careful and systematic control over the effects of metal complexation at 25°C and under conditions where the ionic strength did not vary by too large a degree, a mechanism for the rabbit muscle myokinase similar to that proposed for the human erythrocyte adenylate kinase.
