Involved in the detoxification of xenobiotics and in the activation of ester and amide prodrugs (PubMed:7980644, PubMed:9169443, PubMed:9490062, PubMed:18762277). Hydrolyzes aromatic and aliphatic esters, but has no catalytic activity toward amides or a fatty acyl-CoA ester (PubMed:7980644, PubMed:9169443, PubMed:9490062, PubMed:18762277). Hydrolyzes the methyl ester group of cocaine to form benzoylecgonine (PubMed:7980644). Catalyzes the transesterification of cocaine to form cocaethylene (PubMed:7980644). Displays fatty acid ethyl ester synthase activity, catalyzing the ethyl esterification of oleic acid to ethyloleate (PubMed:7980644). Converts monoacylglycerides to free fatty acids and glycerol. Hydrolyzes of 2-arachidonoylglycerol and prostaglandins (PubMed:21049984). Hydrolyzes cellular cholesteryl esters to free cholesterols and promotes reverse cholesterol transport (RCT) by facilitating both the initial and final steps in the process (PubMed:18762277, PubMed:16024911, PubMed:11015575, PubMed:16971496). First of all, allows free cholesterol efflux from macrophages to extracellular cholesterol acceptors and secondly, releases free cholesterol from lipoprotein-delivered cholesteryl esters in the liver for bile acid synthesis or direct secretion into the bile (PubMed:18762277, PubMed:18599737, PubMed:16971496). a carboxylic ester + H2O = a carboxylate + an alcohol + H(+) 4-methylumbelliferyl acetate + H2O = 4-methylumbelliferone + acetate + H(+) a cholesterol ester + H2O = a fatty acid + cholesterol + H(+) cholesteryl (9Z-octadecenoate) + H2O = (9Z)-octadecenoate + cholesterol + H(+) 2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-glycerol + H2O = (5Z,8Z,11Z,14Z)-eicosatetraenoate + glycerol + H(+) H2O + prostaglandin E2 1-glyceryl ester = glycerol + H(+) + prostaglandin E2 H2O + prostaglandin F2alpha 1-glyceryl ester = glycerol + H(+) + prostaglandin F2alpha Activated by CHAPS (PubMed:9490062). Inhibited by chlorpyrifos oxon (IC(50)=0.21 nM), paraoxon (IC(50)=0.29 nM), or methyl paraoxon (IC(50)=49 nM) (PubMed:18762277). kcat is 59 min(-1), 29 min(-1), 90 min(-1) with 2-arachidonoylglycerol, prostaglandin F2alpha 1-glyceryl ester and prostaglandin E2 1-glyceryl ester as substrates, respectively. Optimum pH is 6.5. Homotrimer and homohexamer. Binds to beta-glucuronidase. Moves from cytoplasm to lipid droplets upon lipid loading. Associates with lipid droplets independently of triglycerides (TG) content of the droplets and hydrolyzes cholesteryl esters more efficiently from mixed droplets. Expressed predominantly in liver with lower levels in heart and lung (PubMed:10562416). Expressed in macrophages (PubMed:11015575, PubMed:21049984, PubMed:18762277). Contains sialic acid. Cleavage of the signal sequence can occur at 2 positions, either between Trp-17 and Gly-18 or between Gly-18 and His-19. Genetic variants in CES1 are associated with clinically significant alterations in pharmacokinetics and drug response of carboxylesterase 1 substrates [MIM:618057]. Belongs to the type-B carboxylesterase/lipase family.