Biosynthesis and Metabolism of Inositol and Inositol Phosphates
- Pp. 16-23 (8)A.K.M. Shamsuddin and Guang-Yu Yang
Water-soluble and non-soluble inositol phosphates and phosphatidylinositol are key constituents of all plants and animals, and participate in their essential metabolic processes. In animal tissues, although the dietary route is one of the three pathways to maintain inositol homeostasis, the receptor mediated salvage pathway involving IMPase 1 and a de novo biosynthetic pathway involving inositol synthase play crucial role in cell signaling and maintaining inositol homeostasis, particularly the polyphosphorylated inositol. Water-soluble inositol polyphosphates including inositol pyrophosphates (up to 60 different possible compounds and at least 37 of these have been found in nature) are extremely important biologically in cell signaling, DNA repair etc. Phosphatidylinositol is the primary source of the arachidonic acid required for biosynthesis of eicosanoids, including prostaglandins via the action of the enzyme phospholipase A2, as well as the main source of diacylglycerols that serve as signaling molecules in animal and plant cells. Phosphatidylinositol is converted to polyphosphoinositides with important signaling and other functional activities in animal cells, and involve a number of different kinases, particularly 3-phosphorylated forms.