Characterization of thiamine diphosphatase in rat small intestine.

The properties of thiamine diphosphatase (TDPase) and p-nitrophenylphosphatase (p-NPPase) in rat small intestine were investigated. TDPase activity, like p-NPPase activity, was high in the mucosa and in the proximal region. Both activities were high in the membrane-associated fractions of the duodenal mucosa. Furthermore, TDPase had the same properties as intestinal alkaline phosphatase (al-Pase). These results suggest that thiamine diphosphate (TDP) and p-nitrophenylphosphate (p-NPP) are hydrolyzed by a single enzyme, al-Pase, in the intestine.