Efflux system for pyridoxine in Schizosaccharomyces pombe

Pyridoxine-charged Schizosaccharomyces pombe released pyridoxine rapidly at 30 degreesC: very low amounts of three other Bg vitamers were also release d. The rate of efflux was temperature-dependent. The initial rate of efflux was dependent on the concentration of pyridoxine in the cells: the rate wa s almost zero at lower than 0.02 mM and became saturated at higher than 0.2 mM. Na+, sodium azide, and dinitrophenol increased the rate in both the pr esence and absence of D-glucose. Mg++, thiamine, and menadione inhibited th e efflux. The intracellular concentration of ATP did not significantly affe ct the efflux rate. The system may be dependent on a membrane potential of the yeast cells. It was found that the fission yeast cells have a gate or c arrier system for efflux of pyridoxine, which was distinct from that in Sac charomyces cerevisiae.