title: Characterization of the specific pyruvate transport system in Escherichia coli K-12.
abstract: A mutant of Escherichia coli K-12 lacking pyruvate dehydrogenase and phosphoenolpyruvate synthase was used to study the transport of pyruvate by whole cells. Uptake of pyruvate was maximal in mid-log phase cells, with a Michaelis constant for transport of 20 microM. Pretreatment of the cells with respiratory chain poisons or uncouplers, except for arsenate, inhibited transport up to 95%. Lactate and alanine were competitive inhibitors, but at nonphysiological concentrations. The synthetic analogs 3-bromopyruvate and pyruvic acid methyl ester inhibited competitively. The uptake of pyruvate was also characterized in membrane vesicles from wild-type E. coli K-12. Transport required an artificial electron donor system, phenazine methosulfate and sodium ascorbate. Pyruvate was concentrated in vesicles 7- to 10-fold over the external concentration, with a Michaelis constant of 15 microM. Energy poisons, except arsenate, inhibited the transport of pyruvate. Synthetic analogs such as 3-bromopyruvate were competitive inhibitors of transport. Lactate initially appeared to be a competitive inhibitor of pyruvate transport in vesicles, but this was a result of oxidation of lactate to pyruvate. The results indicate that uptake of pyruvate in E. coli is via a specific active transport system.
mesh_terms: D000409:Alanine / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008773:Methylphenazonium Methosulfate / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D017866:Phosphotransferases (Paired Acceptors); D011773:Pyruvates / Q000378:metabolism*; D019289:Pyruvic Acid; D013997:Time Factors
chemical_list: D007773:Lactates; D011773:Pyruvates; D008773:Methylphenazonium Methosulfate; D019344:Lactic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; C017092:bromopyruvate; D019289:Pyruvic Acid; D010770:Phosphotransferases; D017866:Phosphotransferases (Paired Acceptors); C022509:pyruvate, water dikinase; D000409:Alanine