PHOSPHORYLATION BY PROTEIN-KINASE-C INACTIVATES AN INOSITOL 1,4,5-TRISPHOSPHATE 3-KINASE PURIFIED FROM HUMAN PLATELETS

被引:16
作者
LIN, AN [1 ]
BARNES, S [1 ]
WALLACE, RW [1 ]
机构
[1] UNIV ALABAMA,DEPT PHARMACOL,BIRMINGHAM,AL 35294
关键词
D O I
10.1016/0006-291X(90)90546-Y
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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 uM) 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. © 1990.
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页码:1371 / 1376
页数:6
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