Abstract
Thiamine-disulfide (TDS) can be reduced to thiamine by papain (Sahashi, Y., Shibazaki, H. : J. Ag. Chem. Soc. Japan 25,57,1950). When TDS or thiamine propyldisulfide (TPD) was incubated with papain at pH 7,25℃ for one hour, formation of thiamine was proportional to the amount of papain added and nearly the equimolar amount of thiamine was obtained from both compounds. The enzymatic activity of papain on α-benzoyl-L-arginineamide after the incubation with TPD or TDS was markedly different. The activity with TPD was about one-tenth of that with TDS. The inhibition of papain activity by other asymmetric disulfide of thiamine such as TTFD or TATD was greater than that by TDS. 50% inhibition of 5mg papain after incubation at pH 7.4,25℃ for 30 minutes was observed with 0.1 μmole TPD or 1 μmole TDS but no inhibition by thiamine or diacetylthiamine. Formation of papain-thiamine complex was demonstrated as a thiochrome-positive spot by paper chromatography of the incubated papain with TDS but no papain-thiamine complex was proved from the incubated papain with TPD. When TPD-S^<35> was incubated with papain, S-propylmercapto-papain complex was demonstrated after its dialysis. By the addition of cysteine the inhibited activity of papain after incubation with TPD was completely recovered to the initial activity of papain.
