Central enzyme in the extracellular metabolism of plasma lipoproteins. Synthesized mainly in the liver and secreted into plasma where it converts cholesterol and phosphatidylcholines (lecithins) to cholesteryl esters and lysophosphatidylcholines on the surface of high and low density lipoproteins (HDLs and LDLs) (PubMed:10329423, PubMed:19065001, PubMed:26195816). The cholesterol ester is then transported back to the liver. Has a preference for plasma 16:0-18:2 or 18:O-18:2 phosphatidylcholines (PubMed:8820107). Also produced in the brain by primary astrocytes, and esterifies free cholesterol on nascent APOE-containing lipoproteins secreted from glia and influences cerebral spinal fluid (CSF) APOE- and APOA1 levels. Together with APOE and the cholesterol transporter ABCA1, plays a key role in the maturation of glial-derived, nascent lipoproteins. Required for remodeling high-density lipoprotein particles into their spherical forms (PubMed:10722751). Catalyzes the hydrolysis of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor or PAF) to 1-O-alkyl-sn-glycero-3-phosphocholine (lyso-PAF) (PubMed:8016111). Also catalyzes the transfer of the acetate group from PAF to 1-hexadecanoyl-sn-glycero-3-phosphocholine forming lyso-PAF (PubMed:8016111). Catalyzes the esterification of (24S)-hydroxycholesterol (24(S)OH-C), also known as cerebrosterol to produce 24(S)OH-C monoesters (PubMed:24620755). a 1,2-diacyl-sn-glycero-3-phosphocholine + a sterol = a 1-acyl-sn-glycero-3-phosphocholine + a sterol ester a 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine + H2O = 1-O-alkyl-sn-glycero-3-phosphocholine + acetate + H(+) (24S)-hydroxycholesterol + 1-hexadecanoyl-2-acyl-sn-glycero-3-phosphocholine = (24S)-24-hydroxycholesterol ester + 1-hexadecanoyl-sn-glycero-3-phosphocholine (24S)-hydroxycholesterol + 1-hexadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine = (24S)-hydroxycholesterol 3-linoleoate + 1-hexadecanoyl-sn-glycero-3-phosphocholine 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphocholine + cholesterol = 1-hexadecanoyl-sn-glycero-3-phosphocholine + cholesteryl (5Z,8Z,11Z,14Z)-eicosatetraenoate 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphocholine + cholesterol = 1-hexadecanoyl-sn-glycero-3-phosphocholine + cholesteryl (9Z-octadecenoate) 1-hexadecanoyl-2-(8Z,11Z,14Z-eicosatrienoyl)-sn-glycero-3-phosphocholine + cholesterol = 1-hexadecanoyl-sn-glycero-3-phosphocholine + cholesteryl (8Z,11Z,14Z)-eicosatrienoate 1-hexadecanoyl-2-(5Z,8Z,11Z-eicosatrienoyl)-sn-glycero-3-phosphocholine + cholesterol = 1-hexadecanoyl-sn-glycero-3-phosphocholine + cholesteryl (5Z,8Z,11Z)-eicosatrienoate 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z,17Z-eicosapentaenoyl)-sn-glycero-3-phosphocholine + cholesterol = (5Z,8Z,11Z,14Z,17Z-eicosapentaenoyl)-cholesterol + 1-hexadecanoyl-sn-glycero-3-phosphocholine 1-hexadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine + cholesterol = 1-hexadecanoyl-sn-glycero-3-phosphocholine + cholesteryl (9Z,12Z)-octadecadienoate 1-hexadecanoyl-2-(6Z,9Z,12Z-octadecatrienoyl)-sn-glycero-3-phosphocholine + cholesterol = (6Z,9Z,12Z-octadecatrienoyl)-cholesterol + 1-hexadecanoyl-sn-glycero-3-phosphocholine 1-hexadecanoyl-2-(11Z,14Z,17Z-eicosatrienoyl)-sn-glycero-3-phosphocholine + cholesterol = (11Z,14Z,17Z-eicosatrienoyl)-cholesterol + 1-hexadecanoyl-sn-glycero-3-phosphocholine 1-hexadecanoyl-2-(9Z,12Z,15Z-octadecatrienoyl)-sn-glycero-3-phosphocholine + cholesterol = (9Z,12Z,15Z-octadecatrienoyl)-cholesterol + 1-hexadecanoyl-sn-glycero-3-phosphocholine 1-hexadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine + H2O = (9Z,12Z)-octadecadienoate + 1-hexadecanoyl-sn-glycero-3-phosphocholine + H(+) 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphocholine + H2O = (5Z,8Z,11Z,14Z)-eicosatetraenoate + 1-hexadecanoyl-sn-glycero-3-phosphocholine + H(+) 1-hexadecanoyl-sn-glycero-3-phosphocholine + a 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine = 1-hexadecanoyl-2-acetyl-sn-glycero-3-phosphocholine + 1-O-alkyl-sn-glycero-3-phosphocholine APOA1 is the most potent activator in plasma (PubMed:19065001, PubMed:8016111). Also activated by APOE, APOC1 and APOA4 (PubMed:19065001, PubMed:8016111). Inhibited by haptoglobin and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) (PubMed:8016111, PubMed:24620755). Affinity for LDL is 2.3 to 4-fold lower than for HDL. Relative reactivities are 16% for HDL(3), 1.3% for HDL(2) and 6.5% for LDL. Secreted into blood plasma (PubMed:3458198, PubMed:8820107, PubMed:10222237). Produced in astrocytes and secreted into cerebral spinal fluid (CSF) (PubMed:10222237). Detected in blood plasma (PubMed:3458198, PubMed:8820107, PubMed:10222237). Detected in cerebral spinal fluid (at protein level) (PubMed:10222237). Detected in liver (PubMed:3797244, PubMed:3458198). Expressed mainly in brain, liver and testes. O- and N-glycosylated. O-glycosylation on Thr-431 and Ser-433 consists of sialylated galactose beta 1-->3N-acetylgalactosamine structures. N-glycosylated sites contain sialylated triantennary and/or biantennary complex structures. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Levels of LCAT activity correlates inversely with leptin levels as well as with obesity for a wide range of BMI values. Belongs to the AB hydrolase superfamily. Lipase family. Lecithin-cholesterol acyltransferase entry