INTERACTION OF ASYMMETRIC DISULFIDE-TYPE THIAMINE WITH PROTEINS

概要

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For proving the formation of protein alkylmercaptan mixed disulfide by the reaction of asymmetric disulfide-type thiamines with the SH-groups of proteins, investigation was made by the method of microassay using HgCl2 and dizithon and the following results were obtained.1. Free thiamine and bound benzyl mercaptan were produced by the incubation of thiamine benzyl disulfide with heat-denatured egg albumin at neutral pH regions but it was not the case with albumin having no reactive SH-groups.2. Similar complexes were formed by the reaction with urea-denatured ovalbumin, bovine serum albumin or β-lactoglobulin. The ratio of the bound mercaptan to free thiamine varied somewhat with the ratio of the reactants (disulfide/protein) and the kind of proteins. It was similar to the ratio of bound thiamine to free thiamine in the reaction of symmetric disulfide-type thiamine, Formation of bound thiamine was not observed in all the proteins.3. From these results it was proved that asymmetric disulfide-type thiamine reacted with protein-SH mainly according to the Equation a. The difference of the reaction mechanism between asymmetric and symmetric disulfide-type thiamines were considered from the view point of thiol-disulfide exchange reaction.
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