Characterization of inositol 1,3,4-trisphosphate phosphorylation in rat liver |
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| Authors: | C A Hansen S vom Dahl B Huddell J R Williamson |
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| Institution: | University of Pennsylvania School of Medicine, Department of Biochemistry and Biophysics, Philadelphia 19104. |
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| Abstract: | Liver homogenates phosphorylated Ins 1,3,4-P3 to an InsP4 isomer that was distinct from Ins 1,3,4,5-P4. This InsP4 isomer accumulated in vasopressin stimulated hepatocytes prelabeled with myo-3H]inositol with a time course that lagged behind Ins 1,3,4-P3 formation. The Ins 1,3,4-P3 kinase responsible for its formation was partially purified from rat liver. The enzyme had a Km for Ins 1,3,4-P3 of 0.29 microM, a Km for ATP of 141 microM and was not affected by changes in free Ca2+ in the physiological range. The relationship of this new InsP4 isomer to the inositol phosphate signaling pathway is discussed. |
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