Escherichia coli cells grown under anaerobic conditions contained an increased level of pyruvate kinase [EC 2. 7. 1. 40] in contrast to a markedly decreased level of nucleoside diphosphate kinase [EC 2. 7. 4. 6]. Pyruvate kinase of E. coli, irrespective of the growth conditions of cells from which the enzyme was derived, showed a broad specificity for nucleoside diphosphates as acceptors of energy-rich phosphate from phosphoenolpyruvate. Cells growing under anaerobic conditions were less sensitive to desdanine, a specific inhibitor of nucleoside diphosphate kinase, than cells growing under aerobic conditions.
These findings strongly suggest that pyruvate kinase takes the place of nucleoside diphosphate kinase in supplying nucleoside triphosphates in E. coli under anaerobic conditions.