Tetrameric alkaline phosphatase from human liver is converted to dimers by phosphatidylinositol phospholipase C.

Membrane-bound human liver alkaline phosphatase solubilized by a non-ionic detergent, Nonidet P-40 (NP-40), has the molecular mass of a tetramer. It can be converted to a dimeric form by treatment with a phosphatidylinositol phospholipase C (PI-PLC) obtained from Bacillus cereus. When human liver plasma membranes were directly treated with PI-PLC, the released alkaline phosphatase was dimeric. Thus, phosphatidylinositol may help maintain the tetrameric quaternary structure of alkaline phosphatase and aid its binding to human liver plasma membranes.