Enzymatic properties of human cytosolic phospholipase A(2)gamma.
The enzymatic properties of cytosolic phospholipase A(2)gamma (cPLA(2)gamma), an isoform of 85-kDa group IV cPLA(2)alpha (cPLA(2)alpha) were studied in vitro and when the enzyme was expressed in cells. cPLA(2)gamma expressed in Sf9 cells is associated with membrane. Membranes isolated from [(3)H]arachidonic acid-labeled Sf9 cells expressing cPLA(2)gamma, constitutively release [(3)H]arachidonic acid. The membrane-associated activity is inhibited by the group IV PLA(2) inhibitor methylarachidonyl fluorophosphonate, but not effectively by the group VI PLA(2) inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. cPLA(2)gamma has higher lysophospholipase activity than PLA(2) activity. Purified His-cPLA(2)gamma does not exhibit phospholipase A(1) activity, but sequentially hydrolyzes fatty acid from the sn-2 and sn-1 positions of phosphatidylcholine. cPLA(2)gamma 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. cPLA(2)gamma overexpressed in lung fibroblasts from cPLA(2)alpha-deficient mice is activated by mouse serum resulting in release of arachidonic, oleic, and palmitic acids, whereas overexpression of cPLA(2)alpha results primarily in arachidonic acid release.
Stewart
Allison
A
Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206, USA.
Ghosh
Moumita
M
Spencer
Diane M
DM
Leslie
Christina C
CC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology*; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D006801:Humans; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera
D017931:DNA Primers; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D011994:Recombinant Proteins; D010741:Phospholipases A