Incorporation of labelled leucine into alkaline phosphatase in response to 1,25-dihydroxycholecalciferol in chick intestinal brush borders.

1,25-Dihydroxycholecalciferol increases the incorporation of leucine into a protein component (Mr = 84000) of the chick intestinal brush-border membrane. Evidence has now been obtained showing this protein to be sub-unit of alkaline phosphatase. Pure chick intestinal alkaline phosphatase was prepared and antibodies raised against it in rabbits. This enzyme and the brush-border protein behaved identically on gel electrophoresis, and in terms of their phosphorylating activity and enzyme activity whether as the enzymically active dimeric form or when reduced to the sub-unit form. The anti-(alkaline phosphatase) reacted with the protein into which the incorporation of leucine was stimulated by 1,25-dihydroxycholecalciferol.