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 Ca 2+. 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.