Abstract
As thiamine and antithiamine compounds were accumulated increasingly on the cells during the time-course of incubation with Kloeckera apiculata in the culture medium, competitive inhibition of cell-uptake of thamine by pyrithiamine or imidazolothiamine compounds was observed at the initial stage of accumulation (Kurata, et al. : Vitamins 36,388,1967). At the later stage of accumulation on larger amounts of the yeast, antithiamine compounds were more completely uptaken by the cells, resulting in less inhibition of thiamine-uptake by cells. At the initial stage of accumulation (5 min.), the cell-uptake of thiamine by Kl. apiculata on incubation with thiamine and antithiamine compounds (both 10^<-6> mole) (A) and the cell-uptake of antithiamine compounds on incubation with Kl. apiculata (B) were estirnated ; the values A/B were compared with their 50% growth inhibition indices ; pyrithiamine 0.51 : 38,benzylimidazolothiamine 1.43 : 380,butylimidazolothiamine 1.60 : 700,imidazolothiamine 1.61 : 3500,triazinothiamine 2.10 : 52000. Fairly close correlation between the values A/B and the inhibition indices was demonstrated as shown in Fig. 2.
