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Lipocortin I and lipocortin II inhibit phosphoinositide‐ and polyphosphoinositide‐specific phospholipase C The effect results from interaction with the substrates
Author(s) -
Machoczek Kathrin,
Fischer Manfred,
Söling Hans-Dieter
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81456-5
Subject(s) - phosphatidylinositol , phospholipase c , annexin , phospholipase , phosphatidylinositol 4,5 bisphosphate , phospholipase a2 , phosphoinositide phospholipase c , biochemistry , chemistry , phosphatidic acid , annexin a1 , phospholipid , phosphatidylserine , cytosol , inositol , pi , phospholipase d , enzyme , membrane , signal transduction , in vitro , receptor
Lipocortins I and II, known to inhibit phospholipase A 2 , have been purified from bovine lung and tested with respect to their ability to affect the enzymatic activities of phosphoinositide‐ and polyphosphoinositide‐specific phospholipase C from human platelets, rat liver cytosol or rat brain membranes. At 0.67,μM, both lipocortins led to complete inhibition of phospholipase C activity with either phosphatidylinositol or phosphatidylinositol 4,5‐bisphophate as substrate. The inhibition could be overcome by increasing the substrate concentration. Ultracentrifugation studies with lipocortin II showed a direct interaction between phosphatidylinositol and the lipocortin, indicating that the lipocortins inhibit phospholipase C not directly but by interacting with the substrate. In experiments with plasma membranes from [ 3 H]inositol‐labeled HL‐60 cells, lipocortin II did not affect PI‐specific phospholipase C activity in the absence or presence of calcium plus or minus GTP‐γ‐S.