LCAT activated by apoA-I catalyzes the reaction of cholesterol and phosphatidylcholine to yield cholesterol esterified with a long-chain fatty acid and 2-lysophosphatidylcholine. While this reaction was first studied in vitro using purified proteins in solution, it occurs in vivo on the surfaces of HDL particles where transiently-bound LCAT is activated by HDL-associated apoA-I protein and consumes HDL-associated cholesterol and phosphatidylcholine. The cholesterol ester reaction product is strongly associated with the HDL particle because of its increased hydrophobicity, while the 2-lysophosphatidylcholine product is released from the particle (Fielding et al. 1972 [2 references]; Adimoolam et al. 1998).