The effect of 1,25 dihydroxycholecalciferol on the ratio of two alkaline phosphatase subunits of Mr 90,000 and 65,000 in adult rat intestine.

The effect of vitamin D3 on the activity of different forms of alkaline phosphatase as well as on the ability of their subunits to form phosphorylated intermediates in the presence of [gamma-32P]ATP was studied. In experiments with rats fed a diet enriched in vitamin D3 phosphatase F3 activity was doubled and the radioactivity of the phosphorylated intermediate of the F3 subunit was greatly enhanced. In contrast, in the case of phosphatase F1 the enzymic activity and the radioactivity of F1 subunit phosphorylated intermediate remained unchanged. In rats fed a vitamin D3-deficient diet, the phosphatase F3 activity was greatly reduced and there were only traces of radioactivity of F3 subunit phosphorylated intermediate.