Abstract
When thiamine benzyldisulfide or thiamine propyldisulfide was incubated with denatured ovalbumin, bovine serum alubumin, or β-lactoglobulin at neutral pH for one hour, formation of free thiamine as well as protein-bound alkylmercaptan was demonstrated. Formation of free mercaptan was also observed in some cases, but no protein-bound thiamine was produced in contrast with the previously reported case of symmetric thiamine disulfide such as O-benzoyl-thiamine disulfide or thiamine disulfide. The ratio of the bound mercaptan to free thiamine slightly varied with the species of protein and was shown to be dependent on the initial molar ratio of the vitamin derivative to protein. From these results it was proved that thiamine alkyldisulfide of asymmetric type reacted with protein-SH mainly as follows, producing protein-alkylmercaptan mixed disulfide. Protein-SH + thiamine-S-S-R &irarr; Protein-S-S-R + thiamine-SH The difference between the reaction patterns of these asymmetric and symmetric thiamine disulfide was briefly discussed.
