Phosphorylation by protein kinase C inactivates an inositol 1,4,5-trisphosphate 3-kinase purified from human platelets.

Academic Article


  • An inositol 1,4,5-trisphosphate 3-kinase purified from human platelets contains two major components, 53 and 36 kDa polypeptides. Each polypeptide expresses Ca2+/calmodulin-dependent enzymatic activity and is phosphorylated by an unidentified protein kinase in the enzyme preparation. The 36-kDa polypeptide may be further phosphorylated on serine residues by protein kinase C to a stoichiometry of 0.8 mole phosphate per mole of protein. Phosphorylation of the 36-kDa component is correlated with inhibition of the kinase activity; the inhibitory effect is dependent upon Ca2+ and phosphatidylserine/diolein and may be blocked by a selective peptide inhibitor of protein kinase C. Phosphorylation by protein kinase C decreases the Vmax of the enzyme from 160 to 28 nmol/mg/min; the Km (0.76 microM) is not altered. These data suggest that protein kinase C may negatively regulate inositol 1,4,5-trisphosphate 3-kinase activity in the human platelet.
  • Keywords

  • Amino Acid Sequence, Animals, Blood Platelets, Cattle, Feedback, Humans, Inositol 1,4,5-Trisphosphate, Molecular Sequence Data, Phosphorylation, Phosphotransferases, Phosphotransferases (Alcohol Group Acceptor), Protein Kinase C
  • Author List

  • Lin AN; Barnes S; Wallace RW
  • Start Page

  • 1371
  • End Page

  • 1376
  • Volume

  • 170
  • Issue

  • 3