H istidine phosphocarrier protein regulates pyruvate kinase A activity in response to glucose in V ibrio vulnificus

Summary The bacterial phosphoenolpyruvate:sugar phosphotransferase system ( PTS ) consists of two general energy‐coupling proteins [enzyme I and histidine phosphocarrier protein ( HPr )] and several sugar‐specific enzyme IIs . Although, in addition to the phosphorylation‐coupled transport of sugars, various regulatory roles of PTS components have been identified in E scherichia coli , much less is known about the PTS in the opportunistic human pathogen V ibrio vulnificus . In this study, we have identified pyruvate kinase A ( PykA ) as a binding partner of HPr in V . vulnificus . The interaction between HPr and PykA was strictly dependent on the presence of inorganic phosphate, and only dephosphorylated HPr interacted with PykA . Experiments involving domain swapping between the PykAs of V . vulnificus and E . coli revealed the requirement for the C ‐terminal domain of V . vulnificus   PykA for a specific interaction with V . vulnificus   HPr . Dephosphorylated HPr decreased the K m of PykA for phosphoenolpyruvate by approximately fourfold without affecting V max . Taken together, these findings indicate that the V . vulnificus   PTS catalyzing the first step of glycolysis stimulates the final step of glycolysis in the presence of glucose through the direct interaction of dephospho‐ HPr with the C ‐terminal domain of PykA .