Considerable differences in steady-state hexokinase specific activity were found in 16 N.C.I.B. strains of Klebsiella aerogenes grown in identical conditions in glucose-limited chemostats. Strains of N.C.I.B. 8258 had no detectable activity, but its glucose-phosphoenolpyruvate phosphotransferase specific activity and that of the other strains were closely similar, and it is concluded that this phosphotransferase activity regulates the overall utilization of glucose, in which hexokinase plays no essential role. The hexokinase activity was subject to regulation by the availability of phosphorus, but this did not affect the glucose phosphotransferase activity. tlactose-grown organisms (including strain N.C.I.B. 8258) had no glucose phosphotransferase activity, but more than adequate hexokinase activity to phosphorylate the intracellularly liberated glucose.
