In vitro synthesis of a constitutive enzyme of Escherichia coli, 6-phosphogluconate dehydrogenase.

Enzymes of central intermediary metabolism are among the constitutive proteins of Escherichia coli. 6-Phosphogluconate dehydrogenase [6-phospho-D-gluconate: nicotinamide adenine dinucleotide phosphate 2-oxidoreductase (decarboxylating), EC 1.1.1.44-A1, an enzyme of the hexose monophosphate shunt, was synthesized in vitro in a coupled transcription-translation system directed by DNA from a specialized transducing phage carrying gnd, the structural gene. Enzyme synthesized in vitro was detected by radiochemical assay of its activity. Kinetic experiments using inhibitors of transcription and translation suggest that synthesis of the mRNA for the enzyme was initiated at the gnd promoter. Neither cyclic AMP nor cyclic GMP had any effect on the amount of enzyme synthesized in vitro.