Abstract
S-benzoylthiamine O-monophosphate (BTMP) is better absorbed from the intestine than thiamine and causes a higher and longer-lasting rise of cocarboxylase level in the liver and blood. In the present studies, the metabolism of BTMP by rat liver and intestine homogenates was investigated. The phosphate group of BTMP was rapidly hydrolyzed by alkaline phosphatase of the intestinal mucosa. The S-benzoyl group of BTMP was found to be hardly decomposed enzymically prior to the hydrolysis of the phosphate group. Available evidence indicated that the phosphate of BTMP inhibited the hydrolysis of S-benzoyl linkage, probably due to steric factors in enzyme-substrate association. As the principal metabolic pathway, BTMP first underwent the dephosphorylation and then S-benzoylthiamine (S-BT) thus produced was converted to thiamine by thioesterase. Due to lower activity of the thioesterase as compared with that of the phosphatase, S-BT was accumlated in the reaction mixture with intestine homogenate. As a possible mechanism of the absorption of orally administered BTMP, it was suggested that BTMP might be transported across the intestinal mucosa after the conversion to S-BT.
