Arachidonoyl Thio-PC is a substrate for many phospholipase A2s (PLA2s) including sPLA2, cPLA2, and iPLA2. Cleavage of the sn-2 fatty acid by PLA2 results in generation of a free thiol which reacts with chromogenic reagents such as DTNB (Ellman’s reagent) and DTP to allow quantitation of PLA2 activity. Isozyme-specific cPLA2 activity can be measured by excluding or inhibiting sPLA2 and iPLA2 activities in the assay.