Metabolism of Ins(1,3,4)P3 by Rat Liver Homogenates
Receptor -mediated PtdIns(4,5)P2hydrolysis directly generates two intracellular mes senger molecules: diacylglycerol, which activates protein kinase C., and Ins(1,4,5)P3, which mobilizes Ca2+ from intracellular stores (see Berridge and Irvine, 1984; Downes and Michell, 1985 for review). Irvineet al. (1984) first recognized the existence of another inositol trisphosphate isomer, Ins(1,3,4)P3. This has now been shown to be the major inositol trisphosphate present following prolonged receptor stimulation in several tissues (Irvineet al., 1985; Burgesset al., 1985; Hansenet al., 1986). Ins(1,3,4)P3arises as a consequence of 5-phosphatase attack on Ins(1,3,4,5)P4, which is itself the product of the phosphorylation of Ins(1,4,5)P3(Irvineet al., 1986a; Hansenet al., 1986). This pathway is probably a major route for the removal of the Ca2+ -mobilizing Ins(1,4,5)P3message from stimulated cells (Irvineet al., 1986a). In addition, Ins(1,3,4,5)P4has been suggested to fulfill a second messenger role inside the cell, by stimulating Ca2+ entry across the plasma membrane (Irvine and Moor, 1986).
KeywordsLiver Homogenate Inositol Phosphate Inositol Trisphosphate Erythrocyte Plasma Membrane Polyphosphate Metabolism
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