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Brevibacteriumflavum mutants defective in the phosphoenolpyruvate (PEP)-dependent glucose phosphotransferase system (PTS) were selected with high frequency by 2-deoxyglucose-resistance. Most of them (DOGr) still had the fructose-PTS and grew not only on fructose but also on glucose like the wild-type strain. A mutant having l/8th the fructose-PTS activity of the wild strain but normal glucose-PTS activity was isolated as a xylitol-resistant mutant. It grew on glucose but not on fructose. The glucose-PTS was active on glucose, glucosamine, 2-deoxyglucose and mannose, and slightly on methyl-a-glucoside and TV-acetylglucosamine, but not on fructose or xylitol. The fructose-PTS acted on fructose and xylitol, and to someextent on glucose but not on glucosamine or 2-deoxyglucose. Mutants unable to grow on glucose (DOGrGlc~)derived from a DOGrmutant were all defective in the fructose-PTS. All revertants able to grow on glucose derived from a DOGrGlc~mutant had the fructose-PTS. The glucokinase activity was about 2/3rds the glucose activity of the fructose-PTS. All the DOGrGlc"mutants had normal levels of glucokinase. One of these mutants grew on maltose and sucrose, which were hydrolyzed to glucose. Thus, glucokinase seems to contribute to the phosphorylation of glucose liberated inside the cell. The fructose-PTS was induced by fructose and repressed by glucose. The glucose repression was not observed in a mutant defective in the glucose-PTS.In Brevibacteriumflavum, an industrial bacterium producing amino acids, glucose is me- 3) The role of glucokinase in glucose metabolism was not revealed. If glucose is phosphorylated solely at the expense of PEP, the theoretical yield in the fermentative production of amino acids synthesized from PEP will be greatly affected. The present paper deals with the derivation of PTS mutants, properties of the individual PTSs and the roles of the PTSs and glucokinase in sugar metabolism.

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