Abstract
Either carbethoxythiamine (CET) or thiamine propyldisulfide (TPD) is stronger in stimulating the growth of Kloeckera apiculata than equimolar thiamine-HCl, but the mode of action is different : CET, when preincubated with Taka-enzyme in the broth, showed the same growth stimulation as that with thiamine or Taka-enzyme treated carbobutoxythiamine. TPD, when preincubated with cysteine in the broth, stimulated the growth better than thiamine with cysteine. TPD, if preincubatad with a suspension of Kloeckera in saline, is easily reduced to thiamine and the yeast centrifuged showed the same growth as that preincubated with thiamine. As shown previously, CET is adsorbed in Kloeckera as CET and the adsorbed yeast showed better growth than thiamine-adsorbed yeast. CET itself gradually reverted into thiamine in the yeast, while TPD when it was added to the broth was quickly reduced to thiamine and yet it is more effective in stimulating the growth than thiamine. Growth-stimulating effects of the two compounds seemed to be based on different mechanisms.
