General characteristics of the transport of several vitamins such as thiamine, riboflavin, pyridoxine and biotin in yeast are described.
These vitamins were taken up by resting yeast cells and retained against concentration gradients, and their transports were dependent on energy, pH, temperature and also displayed structural specificity and saturation kinetics.
It was shown that yeast cells contain, besides a specific system for the uptake of each vitamin, one for its efflux from the cells. The addition of vitamin such as thiamine, riboflavin, and biotin in the medium appeared to repress the synthesis of their transport components during growth. On the other hand, overshoot observed in the transports of pyridoxine and biotin was considered a fast regulatory mechanism by which cells prevent the accumulation of excessive vitamins.
