Abstract
The transketolase activity in the wild strains and thiamine-less mutants of E. coli was determined with or without addition of thiamine diphosphate by a slightly modified method of Racker. The relation of the enzyme activities with thiamine content in the cells was investigated after grown by adding different concentrations of thiamine in the medium. 1) While thiamine contents of E. coli W and K12 grown with 10^<-6>M thiamine were 3 times as much as those of the cells grown without thiamine, no change in the amount of total transketolase in the cells was observed. The holo-enzyme estimated without TDP addition of the cells grown without thiamine showed 50-60% of the total enzyme activities. 2) When thiamine-less mutants, KG 33 or WTh- strain was grown with 10^<-6>M thiamine, they showed 19 or 21 fold higher thiamine content respectively than in those grown with minimum concentration of thiamine ( 10^<-8>M) . 3) Holo-transketolase activities in the mutants grown with 10^<-8>M thiamine showed only 5% of the total enzyme, while holo-enzyme in the mutants grown with 10^<-6>M thiamine showed 70-80% of the total enzyme. However, total enzyme activities estimated with addition of TDP had no change in both strains grown with 10-8M thiamine or 10-6M thiamine. 4) These results suggested that the synthesis of transketolase in the wild and mutants strains of E. coli has neither impaired nor induced by cellular thiamine contents. (Received July 7,1971)
