EC - Sterol O-acyltransferase

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IntEnz Enzyme Nomenclature


Accepted name:
sterol O-acyltransferase
Other names:
acyl coenzyme A-cholesterol-O-acyltransferase
acyl-CoA:cholesterol acyltransferase
acylcoenzyme A:cholesterol O-acyltransferase
cholesterol acyltransferase
cholesterol ester synthase
cholesterol ester synthetase
cholesteryl ester synthetase
sterol-ester synthase
sterol-ester synthetase
acyl-CoA:cholesterol O-acyltransferase
Systematic name:
long-chain acyl-CoA:sterol O-acyltransferase



The enzyme catalyses the formation of sterol esters from a sterol and long-chain fatty acyl-coenzyme A. The enzyme from yeast, but not from mammals, prefers monounsaturated acyl-CoA. In mammals the enzyme acts mainly on cholesterol and forms cholesterol esters that are stored in cytosolic droplets, which may serve to protect cells from the toxicity of free cholesterol. In macrophages, the accumulation of cytosolic droplets of cholesterol esters results in the formation of 'foam cells', a hallmark of early atherosclerotic lesions. In hepatocytes and enterocytes, cholesterol esters can be incorporated into apolipoprotein B-containing lipoproteins for secretion from the cell.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0034736
CAS Registry Number: 9027-63-8
UniProtKB/Swiss-Prot: (15) [show] [UniProt]


  1. Spector, A.A., Mathur, S.N. and Kaduce, T.L.
    Role of acylcoenzyme A: cholesterol O-acyltransferase in cholesterol metabolism.
    Prog. Lipid Res. 18 : 31-53 (1979). [PMID: 42927]
  2. Taketani, S., Nishino, T., Katsuki, H.
    Characterization of sterol-ester synthetase in Saccharomyces cerevisiae.
    Biochim. Biophys. Acta 575 : 148-155 (1979). [PMID: 389289]
  3. Lee, O., Chang, C. C., Lee, W., Chang, T. Y.
    Immunodepletion experiments suggest that acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) protein plays a major catalytic role in adult human liver, adrenal gland, macrophages, and kidney, but not in intestines.
    J. Lipid Res. 39 : 1722-1727 (1998). [PMID: 9717734]
  4. Yang, H., Cromley, D., Wang, H., Billheimer, J. T., Sturley, S. L.
    Functional expression of a cDNA to human acyl-coenzyme A:cholesterol acyltransferase in yeast. Species-dependent substrate specificity and inhibitor sensitivity.
    J. Biol. Chem. 272 : 3980-3985 (1997). [PMID: 9020103]
  5. Chang, C. C., Lee, C. Y., Chang, E. T., Cruz, J. C., Levesque, M. C., Chang, T. Y.
    Recombinant acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) purified to essential homogeneity utilizes cholesterol in mixed micelles or in vesicles in a highly cooperative manner.
    J. Biol. Chem. 273 : 35132-35141 (1998). [PMID: 9857049]
  6. Das, A., Davis, M. A., Rudel, L. L.
    Identification of putative active site residues of ACAT enzymes.
    J. Lipid Res. 49 : 1770-1781 (2008). [PMID: 18480028]

[EC created 1972, modified 2019]