Abstract
In the previous report, it was confirmed that the respiration of baker's yeast was stimulated by the addition of a large amount of thiamine and was inhibited with sorbate, however, the co-existence of thiamine and sorbate had a significant inhibitory effect on the respiration. In the present report, the mechanism of the remarkable inhibition is studied. The addition of a large amount of thiamine in the growth medium resulted the decrease of CoA level in the cells and the CoA synthesizing ability of the enzymes, extracted from the cells, showed significant decrease compared with the control cells. At in vitro CoA synthesizing enzyme reaction, the addition of a large amount of thiamine also caused the decrease of the CoA formation and major part of the inhibition would be attributed to that of pantothenate kinase. From above results the possible mechanism of the remarkable inhibition is considered that the shortage of CoA on account of the formation of sorbyl-CoA and the decrease of the supplement of CoA with thiamine result the inhibition of the respiration.
