抄録
Bakers' yeast extract containing alcohol dehydrogenase was incubated with 0.5 mM DPN and 3.8 mM dihydrothiamine at pH 8.5 and reduction of DPN (increase of absorption at 340 mμ) was observed whereas no formation of thiamine was detected. Dihydrothiamine was greatly decomposed even at the presence of boiled yeast extract and simultaneously DPN was reduced probably by mercaptol derived from dihydrothiamine. Either peroxidase from horse-radish with hydrogen peroxide and guaiacol or lipoxidase from soy bean with linoleate was capable to oxidize dihydrothiamine into thiamine to the extent of 3-20% (in peroxidase) or 1-4% (in lipoxidase). Simultaneous decomposition of dihydrothiamine also occurred to much greater extents corresponding to durations of its incubating time.
