Properties of the lactose transport system in Klebsiella sp. strain CT-1.
Highly purified [D-glucose-1-14C]lactose has been used to study the transport of lactose by Klebsiella sp. strain CT-1. Strain CT-1 transports lactose by a lactose-inducible system that exhibited an apparent Km of 6 mM lactose and an apparent Vmax of 140 nmol/min per mg of cell protein. Lactose uptake was inhibited competitively by o-nitrophenyl-beta-D-galactoside with a Ki value of 8 mM, but was not inhibited by thio-beta-methyl-galactoside. D-Glucose, D-mannose, 2-deoxyglucose, and alpha-methyl-D-glucoside also inhibited lactose uptake. Phosphoenolpyruvate-dependent hydrolysis of o-nitrophenyl-beta-D-galactoside and lactose-dependent release of pyruvate from phosphoenolpyruvate by benzene-treated CT-1 cells showed that CT-1 transports lactose by a phosphoenolpyruvate:sugar phosphotransferase system. Correlations between the growth rate of CT-1 on lactose and properties of the transport system indicated that transport is the rate limiting step in utilization of lactose.
D001692:Biological Transport / Q000187:drug effects; D002241:Carbohydrates / Q000494:pharmacology; D007700:Kinetics; D007709:Klebsiella / Q000254:growth & development / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D009598:Nitrophenylgalactosides / Q000494:pharmacology; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism
D002241:Carbohydrates; D009598:Nitrophenylgalactosides; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D007785:Lactose