The relationship of alkaline phosphatase, CaATPase, and phytase

Alkaline phosphatase, highly purified from bovine intestinal mucosa, has significant hydrolytic activity against phytate and CaATP. Phytase and CaATPase activities require quite different assay conditions than those which are optimal for conventional alkaline phosphatase substrates such as 4-nitrophenyl phosphate. We have used affinity chromatography and antibody recognition to demonstrate that the phytase and CaATPase activities are not due to contaminating enzymes, but are intrinsic activities of intestinal alkaline phosphatase. All of the phytase and CaATPase activities present in crude extracts of bovine intestinal mucosa can be accounted for by alkaline phosphatase. Apparently neither phytase nor CaATPase exist in this tissue as independent enzymes. Specific substrates which require assay conditions quite different from the conventional 4-nitrophenyl phosphate substrate may account for the physiological function of "alkaline phosphatase."