cytosolic phospholipase A2 beta; cPLA2-beta; phospholipase A2 group IVB (PLA2G4B)
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Function
- Ca+2-dependent phospholipase A2
- selectively hydrolyzes glycerophospholipids in the sn-2 position with a preference for arachidonoyl phospholipids
- much weaker activity than PLA2G4A
- isoform 3 has Ca+2-dependent activity against palmitoyl- arachidonyl-phosphatidylethanolamine & low level lysophospholipase activity, but no activity against phosphatidylcholine
- stimulated by cytosolic Ca+2
- N-terminal C2 domain associates with lipid membranes
- Vmax=7.9 pmol/min/mg enzyme (isoform 1)
- Vmax=3.6 pmol/min/ug enzyme with cAMP as substrate (isoform 4)
- Vmax=140 nmol/min/ug enzyme with 1-[14C]16:0-2-lyso-PC as substrate (isoform 1)
- Vmax=1.6 nmol/min/ug enzyme with 1-[14C]16:0-2-lyso-PC as substrate (isoform 3)
- Vmax=2.1 nmol/min/ug enzyme with 1-16:0-2-[14C]20:4-PC as substrate (isoform 1)
- Vmax=0.6 nmol/min/ug enzyme with 1-16:0-2-[14C]20:4-PE as substrate (isoform 1)
- Vmax=0.8 nmol/min/ug enzyme with 1-16:0-2-[14C]20:4-PE as substrate (isoform 3)
- Vmax=0.3 nmol/min/ug enzyme with 1-16:0-2-[14C]18:2-PE as substrate (isoform 3)
Structure
- contains 1 C2 domain
- contains 1 PLA2c domain
Compartment
- cytoplasm
- isoform 3: mitochondrial membrane; peripheral membrane, early endosomal membrane
- translocates to membrane vesicles (Ca+2-dependent)
Alternative splicing
named isoforms=4
Expression
- widely expressed, including brain, heart, liver, cerebellum, pancreas
- isoform 3 is widely expressed
- most tissues also express read-through transcripts from this gene into the upstream gene (JMJD7), some of which may encode fusion proteins