Effect of lipids on App1p PAP activity. PAP activity was measured in the absence and presence of the indicated surface concentrations of phospholipids (A) and sphingolipids (B). The surface concentration of PA was 2.5 mol % (molar concentration of 0.2 mm). The data shown are means ± S.D. (error bars) from triplicate enzyme determinations. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PS, phosphatidylserine; CDG, CDP-diacylglycerol; PG, phosphatidylglycerol; CL, cardiolipin; Sa, sphinganine; SaP, sphinganine 1-phosphate; Cer, ceramide; CerP, ceramide 1-phosphate.