Characterization of inositol 1,3,4-trisphosphate phosphorylation in rat liver.
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.
Hansen
C A
CA
University of Pennsylvania School of Medicine, Department of Biochemistry and Biophysics, Philadelphia 19104.
vom Dahl
S
S
Huddell
B
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Williamson
J R
JR
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D007536:Isomerism; D008094:Lithium / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000032:analysis; D017853:Phosphotransferases (Alcohol Group Acceptor); D051381:Rats; D013403:Sugar Phosphates / Q000378:metabolism*
D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D008094:Lithium; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C056875:myo-inositol-trisphosphate 6-kinase