Cited by 169Cholesterol and Lipid MetabolismLipid metabolism and disordersLipid Membrane Structure and Behavior

Human plasma lecithin-cholesterol acyltransferase. An elucidation of the catalytic mechanism.

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Jauhiainen, M, Dolphin, P J·1986·Journal of Biological Chemistry

Abstract

Human plasma lecithin-cholesterol acyltransferase (LCAT) transacylates the sn-2 fatty acid of lecithin to cholesterol forming cholesteryl ester and lysolecithin. Measurement of the phospholipase A2 and transacylase activities of the enzyme using proteoliposome substrates and following selective chemical modification of serine, histidine, and cysteine residues of pure homogeneous LCAT indicated the following catalytic mechanism: HS-Cys-E-Ser-OH + lecithin in equilibrium HS-Cys-E-Ser-O-FA + lysolecithin, HS-Cys-E-Ser-O-FA in equilibrium FA-S-Cys-E-Ser-OH, FA-S-Cys-E-Ser-OH + cholesterol-OH in equilibrium HS-Cys-E-Ser-OH + cholesterol-O-FA, where FA denotes fatty acid. Modification of 2 LCAT cysteine residues with 5,5'-dithiobis-(2-nitrobenzoic acid) or treatment with ferricyanide inactivated the transacylase but not the phospholipase A2 activity. Modification of 1 serine residue with phenylmethanesulfonyl fluoride or 1 histidine residue with diethyl pyrocarbonate inhibited cholesteryl ester formation and phospholipase A2 activity. Proteoliposome substrates protected both activities against chemical inactivation. Lecithin alone protected the phospholipase A2 activity against phenylmethanesulfonyl fluoride inactivation but not the transacylase against 5,5'-dithiobis-(2-nitrobenzoic acid) inactivation. Incubation of native LCAT with arachidonyl-CoA or the lecithin-apo-A-I proteoliposome resulted in acylation of three enzyme sites, only one of which was stable to neutral hydroxylamine after denaturation. Fatty acylenzyme oxy- and thioesters were demonstrable in both cases. No transfer of arachidonic acid from iodoacetamide-modified LCAT to cholesterol occurred, indicating that the fatty-acylated serine residue cannot directly esterify cholesterol. Cholesterol arachidonate was formed upon incubation of phenylmethanesulfonyl fluoride-modified LCAT with arachidonyl-CoA.

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Crossref · 10.1016/s0021-9258(19)62718-3

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Authors
Jauhiainen, M., & Dolphin, P. J.
Affiliations
Dalhousie University (CA)
Venue
Journal of Biological Chemistry
Publisher
Elsevier BV
Published
1986-05
Volume
261
Issue
15
Pages
7032-7043
ISSN
0021-9258 (ISSN-L)
OpenAlex
W1480395470
Cited by
169
References
56
Citations by year
2026: 1 · 2025: 3 · 2023: 1 · 2022: 1 · 2021: 1 · 2020: 3 · 2019: 2 · 2018: 3 · 2017: 2 · 2016: 2 · 2015: 4 · 2014: 4 · 2013: 3 · 2012: 4
FWCI
17.68
Type
journal article
Language
en
Open access
Locations
  • Journal of Biological Chemistry (publishedVersion, cc-by)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Surgery › Cholesterol and Lipid Metabolism
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Lipid metabolism and disorders
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Lipid Membrane Structure and Behavior
Keywords
lecithin:cholesterol acyltransferase, catalytic mechanism, phospholipase A2 activity, cholesteryl ester formation, lysophosphatidylcholine, enzyme inactivation, serine residues, histidine residues, cysteine residues, arachidonic acid, apolipoprotein A-I, proteoliposomes
MeSH terms
Acyltransferases, Cysteine, Dithionitrobenzoic Acid, Humans, Kinetics, Phosphatidylcholine-Sterol O-Acyltransferase, Liposomes, Phospholipases A, Protein Binding, Proteolipids, Phospholipases A2

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