The irreversibility of thiamin transport inSaccharornyces cerevisiae

Neither exit nor counterflow efflux of thiamin, taken up previously by an active transport, were found in Saccharomyces cerevisiae, in either the wild type or a mutant with a lower rate of thiamin phosphorylation. Complete inhibition of thiamin phosphorylation by oxythiamin did not lead to any release of thiamin taken up by the cell.