ROLE OF PHOSPHOENOLPYRUVATE IN THE CATABOLITE REPRESSION OF TRYPTOPHANASE SYNTHESIS IN ESCHERICHIA COLI

Abstract

Catabolite repression of tryptophanase synthesis in E. coli K12 TAB40 was examined. The supply of glycerol or pyruvate to cells grown on each alternative carbon source reduced incorporation of either into the cells. Thus the synergistic effect on the catabolite repression of tryptophanase synthesis by combined supply of glycerol and pyruvate was presumed to be the result of metabolic alteration due to the alternative supply of the carbon source. Addition of arsenite to glycerol-grown cell repressed the tryptophanase formation. On the other hand, addition of arsenite to the pyruvate-grown cell derepressed the enzyme formation. This phenomenon was also seen in β-galactosidase system. Catabolite repression caused by glycerol plus pyruvate, therefore, was considered to be governed by the balance between glycolysis and gluconeogenesis. Intracellular pool of phosphoenolpyruvate (PEP) increased when catabolite repression was brought about, but little pool was seen when not repressed. ATP and FDP pool showed no appreciable change whether the repression was present or not. Conclusively PEP is assumed to play an important role in catabolite repression.