抄録
1. The amounts of protein-thiamine mixed disulfide produced by the reaction of thiamine or O-benzoyl thiamine (OBT) with oxidized egg albumin at various pH levels were determined. The formation of the bound form of thiamine was detected at pH about 7.0, increasing suddenly at pH above 8.2, and reaching a nearly constant value at pH above 10.0. The pH-curve was in good agreement with the curve of pH and formation of the thiol form, showing the parallelism between the production of the bound form and the concentration of the thiol type thiamine.
2. OBT showed already the reactivity at pH around 6.0, and more amounts were bound with protein than thiamine at any pH levels.
3. The equilibrium concentrations of the thiol form of thiamine and of OBT were compared in weakly alkaline range by measuring the anodic wave height of polarography. The anodic wave height of OBT was found to be far higher than that of thiamine, showing that OBT was more liable to take the thiol form. These findings suggest that the difference in the reactivities of thiamine and OBT in weakly alkaline range is mainly due to the difference in the formation of the thiol form.
