Pyruvate formation during the catabolism of simple hexose sugars by Escherichia coli: studies with pyruvate kinase-negative mutants

Abstract

Escherichia coli K-12 mutants lacking the adenosine 5'-monophosphate-activated pyruvate kinase have been isolated accidentally and used to prepare further mutants additionally devoid of the fructose bisphosphate-activated pyruvate kinase. Such double mutants totally devoid of pyruvate kinase activity still grow well under aerobic conditions on sugars that are catabolized by the phosphoenolpyruvate (PEP):sugar phosphotransferase system, but they grow poorly on non-phosphotransferase system sugars. This suggests that although pyruvate kinase plays a major role in the formation of pyruvate from PEP during growth on non-phosphotransferase system sugars, the operation of the PEP:sugar phosphotransferase system can contribute significantly to pyruvate production from PEP. In the absence of pyruvate kinase and an active PEP:sugar phosphotransferase system the methylglyoxal glycolytic bypass may also function to some extent for the formation of pyruvate during the catabolism of simple hexose sugars. No unique physiological role can yet be ascribed to the adenosine 5'-monophosphate-activated pyruvate kinase as a result of these studies.