Roles of C-Terminal Processing, and Involvement in Transacylation Reaction of Human Group IVC Phospholipase A2 (cPLA2 )

Phospholipases A2 (PLA2) are a diverse group of enzymes that hydrolyze the sn-2 fatty acids from phospholipids and play a role in a wide range of physiological functions. A 61-kDa calcium-independent PLA2, termed cPLA2γ, was identified as an ortholog of cPLA2α with approximately 30% overall sequence identity. cPLA2γ contains a potential prenylation motif at its C terminus and is known to have PLA2 and lysophospholipase activities, but its physiological roles have not been clarified. In the present study, we expressed various forms of recombinant cPLA2γ, including non-prenylated and noncleaved forms, in order to investigate the effects of C-terminal processing. We examined the expression of wild type and non-prenylated (SCLA) forms of cPLA2γ and found that the SCLA form was expressed normally and retained almost full activity. Expression of prenylated and non-cleaved form of cPLA2γ using yeast mutants lacking the prenyl protein proteases AFC1 (a-factor converting enzyme) and RCE1 (Ras converting enzyme) revealed decreased expression in the mutant strain compared to that in wild type yeast, suggesting that complete C-terminal processing is important for the functional expression of cPLA2γ. In addition, cPLA2γ was found to have coenzyme A (CoA)-independent transacylation and lysophospholipid (LPL) dismutase (LPLase/transacylase) activities, suggesting that cPLA2γ may be involved in fatty acid remodeling of phospholipids and clearance of toxic lysophospholipids in the cells.