Purity >98%. Thioester analogs of glycerophospholipids, in combination with Ellman's reagent, are convenient colorimetric substrates for the measurement of phospholipase (PL) activity. Diheptanoyl thio-PC is a commonly-used colorimetric substrate for all PLA2 s, with the exception of cPLA2 and platelet-activating factor acetylhydrolase (PAF-AH). Heptanoyl thio-PC is an analog of diheptanoyl thio-PC that contains an ether-linked saturated C16 moiety at the sn -1 position rather than a heptanoyl thiol ester. Porcine pancreatic and bee venom sPLA2 enzymes exhibit 10-13 fold less activity when assayed with heptanoyl thio-PC compared to diheptanoyl thio-PC. This decrease in activity has not been thoroughly investigated.