抄録
As shown in the previous paper, asymmetric disulfides of thiamine are inhibitors of papain and also have been proved to be specific inhibitors to yeast alcohol dehydrogenase (YADH) : When 2 mg of purified YADH was incubated with 1μmole TPD at pH 6 or 7 for 3 hours, the activity was reduced to 68% or 60% of the initial one but the activity with TDS, diacetylthimine (DAT) or thiamine was slightly reduced when incubated at pH 6 or 7. On incubation at pH 8,TDS and DAT showed 64% or half inhibition while thiamine itself inhibited YADH to the extent of 20%. The inhibition with TPD was recovered halfly by addition of 100μmole cysteine. Formation of thiamine by incubation of YADH with TPD or TDS was equimolar in either compound but it was negligibly small by that with DAT at pH 6 or 7. Formation of thiamine was greater at pH 8 in each compound but was not proportional to the inhibition in the cases of TDS and TPD. Thiamine was also demonstrated on incubation of inactivated YADH by either heat or preservation for long time with TPD. Formation of YADH-thiamine complex was demonstrated by means of paper chromatography only on the incubated YADH with TDS, but not with TPD. Formation of S-propylmercapto-YADH by incubation of YADH with TPD was indirectly proved by detection of S-propylmercapto-cysteine on paper chromatogram of the incubated YADH when it was reduced cysteine.
