Expression of pyruvate formate-lyase of Escherichia coli from the cloned structural gene

It is shown here that a plasmid (p29) derived from the transducing phage lambda aspC2 (Christiansen and Pedersen 1981) codes for pyruvate formate-lyase. The identity of the 80 kilodaltons (kd) gene product of plasmid p29 with the pyruvate formate-lyase polypeptide was proven (i) by co-migration of the gene product expressed in the maxicell system with purified enzyme on O'Farrell gels, and (ii) by comparison of the peptide maps obtained from limited proteolysis. In vivo the 80 kd form of the enzyme was proteolytically converted to a 78 kd polypeptide. The two polypeptides (80 kd and 78 kd) and their charge isomers present in purified enzyme preparations are therefore products of a single gene. Aerobically grown cells of Escherichia coli contained a basal level of pyruvate formate-lyase which was derepressed 5- to 10-fold under anaerobiosis. Derepression also occurred during anaerobic growth on glycerol plus fumarate. Presence of plasmid p29 caused overproduction of pyruvate formatelyase, 11-fold upon anaerobic growth on glucose, 14-fold upon aerobic growth on glucose and 33-fold upon aerobic growth at the expense of D-lactate.