A mutant phosphoenolpyruvate carboxykinase in Escherichia coli conferring oxaloacetate decarboxylase activity.

The phosphoenolpyruvate carboxykinase in Escherichia coli (encoded by pck) catalyzes the conversion from oxaloacetate (OAA) to phosphoenolpyruvate under gluconeogenic conditions. We report here the characterization of two mutant alleles, pck-51 and pck-53, both of which are point mutations leading to single amino acid changes (D to N at position 268 and G to S at position 284, respectively). Pck51 is an altered-activity mutant that catalyzes the conversion from OAA to pyruvate (OAA decarboxylase activity). This new activity was not detected from the wild-type Pck, and it complements the pck null mutation only in a pps+ background. Pck53 is a reduced-activity mutant that complements the pck null mutation in a strain-dependent fashion.