Biochemistry and genetics of inositol phosphate metabolism in Dictyostelium

Biochemical and genetic data on the metabolism of inositol phosphates in the microorganism Dictyostelium are combined in a scheme composed of in five subroutes. The first subroute is the inositol cycle as found in other organisms:inositol is incorporated into phospholipids that are hydrolysed by PLC producing Ins(1,4,5)P-3 which is dephosphorylated to inositol, The second subroute is the sequential phosphorylation of inositol to InsP(6); the Ins(3,4,6)P-3 intermediate does not release Ca2+. The third subroute is the sequential phosphorylation of Ins(1,4,5)P-3 to InsP(6) in a nucleus associated fraction, whereas the fourth subroute is the dephosphorylation of Ins(1,3,4,5,6)P-5 to Ins(1,4,5)P-3 at the plasma membrane, This last route mediates Ins(1,4,5)P-3 formation in cells with a disruption of the single PLC gene. Finally, we recognize the formation of InsP(7) and InsP(8) as the fifth subroute. (C) 1997 Federation of European Biochemical Societies