Changes of the molecular organization induced by the lipidic microenvironment in the alkaline phosphatase activity reconstituted in liposomes: kinetic mechanism of enzyme regulation

Abstract

The biological membrane organization in micro-domains has a key role in many cellular processes similar to proteic receptors and signal transduction.The existence of micro-domains, also called rafts, has been explained by the separation of lipidic membranes in two phases: liquid crystalline and ordinate liquid phase, rich in cholesterol and sphingolipids. Microscopy studies of atomic force, have recently demonstrated the spontaneous insertions of alkaline phosphatase, via glycosylphosphatidylinositol (GPI) anchor, to micro-domains in ordinate phase or cholesterol rich.Besides that, it has already been demonstrated in our laboratory that the catalytic properties of alkaline phosphatase vary depending upon which microenvironment the enzyme is located.Then, this project intends to correlate the control mechanisms of alkaline phosphatase activity with the intermolecular organization and the membrane lipids phase state. The modulation of the activity of the enzyme in different lipidic microenvironments (cholesterol, phospholipids and sphingolipids) will be studied as a regulation mechanism and transduction among enzymes which do not share common intermediate metabolites.That is, to verify how molecular organization changes, induced by cholesterol and/or other lipids, can modulate the activity of enzymes by regulating the production of secondary lipidic messengers and/or fusion processes and topologic recombination of the lipidic bilayer, concomitantly modeling alkaline phosphatase activity. In this way, these studies can bring significant knowledge advance of enzyme role as much as of the biomineralization process. (AU)