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 phosphoenolpy ruvate under gluconeogenic conditions. We report here the characteriza tion 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 26 8 and G to S at position 284, respectively). Pck51 is an altered-activ ity mutant that catalyzes the conversion from OAA to pyruvate (OAA dec arboxylase activity). This new activity was not detected from the wild -type Pck, and it complements the pck null mutation only in a pps(+) b ackground. Pck53 is a reduced-activity mutant that complements the pck null mutation in a strain-dependent fashion.