Characterization of the oxaloacetate decarboxylase and pyruvate kinase-like activities of Saccharomyces cerevisiae and Anaerobiospirillum succiniciproducens phosphoenolpyruvate carboxykinases

Two members of the ATP-dependent class of phosphoenolpyruvate carboxykinase s (PEPCKs) (Saccharomyces cerevisiae and Anaerobiospirillum succiniciproduc ens) have been comparatively studied with regard to their oxaloacetate (OAA ) decarboxylase and pyruvate kinase-like activities. The pyruvate kinase-li ke activities were dependent on the presence of Mn2+; at the same concentra tions Mg2+ was not effective. These activities were synergistically activat ed by a combination of both metal ions. V-max, for these activities in A. s ucciniciproducens and S. cerevisiae PEPCKs was 0.13% and 1.2% that of the p rincipal reaction, respectively. The OAA decarboxylase activity was nucleot ide independent and, with decreasing order of effectiveness, these activiti es were supported by Mn2+ and Mg2+. AMP is an activator of these reactions. V-max for the OAA decarboxylase activities in A. succiniciproducens and S. cerevisiae PEPCKs was 4% and 0.2% that of the PEP-forming reaction, respec tively.