Unlabeled lipoproteins (400 μg each) were first treated with SMase, followed by heat-inactivation of SMase, as described in the text. The SM-depleted and intact lipoproteins were then incubated with recombinant HL (32 μg protein) for 4 h at 37 °C.The lipids were extracted after adding an internal standard (17:0–17:0 PC) and the PC composition was analyzed by LC/MS/MS as described in the text, by MRM. The decrease in PC amount was calculated from the difference in the total PC between control (no HL) and experimental (with HL) samples. Values shown are mean ±SEM of 6 analyses (HDL) or 4 analyses (for VLDL and LDL), but were all obtained from the same batch of the enzyme..
* p< 0.05 compared to HDL; # p< 0.05 HL vs SMase + HL.