A P-31 NUCLEAR-MAGNETIC-RESONANCE INVESTIGATION OF ACYL GROUP-TRANSFER FROM PHOSPHATIDYLCHOLINE TO YIELD LYSOPHOSPHATIDYLCHOLINE IN HUMAN PLASMA

P-31 nuclear magnetic resonance (NMR) spectroscopy was used to measure the rate of acyl transfer from phosphatidylcholine (lecithin, PC) in whole plasma and in high density lipoprotein (HDL). Spectral deconvolu tion was used to resolve overlapping resonances in the P-31 MMR spectr a of the phospholipids. Mean values of the acyl group transfer rates f rom PC in plasma and HDL were 36 mu mol L(-1)h(-1) and 19 mu mol L(-1) h(-1), respectively. The reciprocal nature of the decrease in the spec tral peak intensities of PC, compared to the increase in the intensiti es of the lysolecithin (lysoPC) peaks, suggested a substrate/product r elationship consistent with the action of lecithin:cholesterol acyltra nsferase (LCAT), the enzyme responsible for the esterification of free cholesterol in plasma. LCAT involvement was confirmed by measuring th e cholesterol esterification rate based on the C-13 MMR spectra obtain ed on lipid extracts from plasma that had been incubated at 37 degrees C. Within experimental error, the rate of lysoPC formation in plasma was shown to be equal to that of cholesteryl ester formation.