title: Kinetic analysis of lecithin:cholesterol acyltransferase activity toward discoidal HDL.
abstract: The kinetics of lecithin:cholesterol acyltransferase(LCAT, EC 2.3.1.43)-catalyzed generation of cholesteryl ester in discoidal high density lipoproteins (HDL) was analyzed in terms of initial binding of LCAT to the disc surface followed by a three-state reaction of the hydrolysis of phosphatidylcholine sn-2 ester bond and acyl-enzyme formation. Cholesterol was considered as alcoholic nucleophile that increases the solvolysis rate of acyl-LCAT. The raw kinetic data of Sparks et al. (J Biol Chem 270:5151-5157, 1995) for four preparations of reconstituted discoidal HDL with a constant level of apolipoprotein A-I and palmitoyloleoylphosphatidylcholine per disc but with cholesterol in a lipid phase continuously increasing from 2.1 to 12.5 mol%, were analyzed in terms of the kinetic equation and a complete set of rate constants was obtained. Data at high cholesterol content do not indicate a saturation phenomenon, thus giving no evidence for a binding of cholesterol to the enzyme. This analysis may be used in the study of LCAT activation by exchangeable apolipoproteins and contribution of the HDL structure.
authors.affiliation: National Research Centre for Preventive Medicine, 10, Petroverigsky Street, 101990, Moscow, Russia. dergunov@img.ras.ru
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Dergunov
mesh_terms: D000465:Algorithms; D002784:Cholesterol / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008074:Lipoproteins; D008075:Lipoproteins, HDL / Q000737:chemistry*; D008956:Models, Chemical; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D008074:Lipoproteins; D008075:Lipoproteins, HDL; C034366:discoidal lipoproteins; D014867:Water; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase