抄録
1. When 10μmoles of thiamine disulfide (TDS) or O-benzoylthiamine disulfide was added to 0.2μmoles of SH-blocked urea-denatured bovine serum albumin and the mixture was incubated at pH 9.0 and 37°, the formation of protein-thiamine mixed disulfide, at most 4.5 moles per mole protein, was observed.
2. This reaction was almost completely inhibited by SH-reagents, such as p-chloromercuribenzoate (PCMB) and N-ethylmaleimide, about 1/10 mole of TDS, whereas it was markedly accelerated by the addition of thiamine, corresponding to 1/50 to 1/10 mole of TDS.
3. In the reaction with iodine-oxidized egg albumin, the formation of similar compound and its inhibition by PCMB were observed.
4. From these results, it was assumed that protein-thiamine mixed disulfides were formed from protein SS-groups and symmetric disulfide-type thiamines by the similar disulfide-disulfide exchange reaction of low molecules catalyzed by a trace amount of thiols.
5. Asymmetric disulfide-type thiamines such as thiamine benzyl disulfide and thiamine propyl disulfide were found to produce both protein-bound thiamine and protein-bound alkylmercaptan under the same conditions.
6. Considering the results of this paper and those of the previous findings, it was concluded that there are three types of exchange reaction between thiamine derivatives and proteins.
