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Calcium is sufficient but not necessary for activation of sheep platelet cytosolic phospholipase A 2
Author(s) -
Zupan Lori A.,
Kruszka Kelly K.,
Gross Richard W.
Publication year - 1991
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(91)80753-p
Subject(s) - phospholipase , calcium , cytosol , phospholipase c , biochemistry , extracellular , calcium in biology , chemistry , intracellular , phospholipase a , platelet , phospholipase a2 , phosphoinositide phospholipase c , enzyme , platelet activation , biology , immunology , organic chemistry
In this study we demonstrate that: (1) although the major phospholipase A 2 present in sheep platelets is activated by calcium ions, it can effectively catalyze hydrolysis of the sn ‐2 ester linkage in phospholipids in the absence of calcium: (2) expression of calcium‐independent phospholipase A 2 activity can be induced by NACl utilizing purified (but not crude) cytosolic enzyme; and (3) calcium‐independent phospholipase A 2 activity is regulated by a reconstitutable cytosolic protein. Collectively, these results underscore the fundamental catalytic differences between extracellular and intracellular calcium‐dependent phospholipases A 2 and demonstrate that calcium is sufficient, but not necessary, for the activation of this class of intracellular phospholipases A 2