Enzymatic Properties of Human Cytosolic Phospholipase A2γ*

By A. Stewart, M. Ghosh, D. Spencer, Christina S. Leslie. Journal of Biological Chemistry, 2002

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The enzymatic properties of cytosolic phospholipase A2γ (cPLA2γ), an isoform of 85-kDa group IV cPLA2α (cPLA2α) were studied in vitro and when the enzyme was expressed in cells. cPLA2γ expressed in Sf9 cells is associated with membrane. Membranes isolated from [3H]arachidonic acid-labeled Sf9 cells expressing cPLA2γ, constitutively release [3H]arachidonic acid. The membrane-associated activity is inhibited by the group IV PLA2 inhibitor methylarachidonyl fluorophosphonate, but not effectively by the group VI PLA2 inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. cPLA2γ has higher lysophospholipase activity than PLA2 activity. Purified His-cPLA2γ does not exhibit phospholipase A1 activity, but sequentially hydrolyzes fatty acid from the sn-2 and sn-1 positions of phosphatidylcholine. cPLA2γ overexpressed in HEK293 cells is constitutively active in isolated membranes, releasing large amounts of oleic, arachidonic, palmitic, and stearic acids; however, basal fatty acid release from intact cells is not increased. cPLA2γ overexpressed in lung fibroblasts from cPLA2α-deficient mice is activated by mouse serum resulting in release of arachidonic, oleic, and palmitic acids, whereas overexpression of cPLA2α results primarily in arachidonic acid release.

Subfields: Cell Biology, Molecular Biology, Pathology and Forensic Medicine

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