sterol O-acyltransferase 1
Identifiers
Symbol	SOAT1
Alt. symbols	ACAT, SOAT, STAT
Entrez	6646
HUGO	11177
OMIM	102642
RefSeq	NM_003101
UniProt	P35610
Other data
EC number	2.3.1.26
Locus	Chr. 1 q25

sterol O-acyltransferase 2
Identifiers
Symbol	SOAT2
Alt. symbols	ACAT2
Entrez	8435
HUGO	11178
OMIM	601311
RefSeq	NM_003578
UniProt	O75908
Other data
EC number	2.3.1.26
Locus	Chr. 12 [1]

Sterol O-acyltransferase (also called Acyl-CoA cholesterol acyltransferase, Acyl-CoA cholesterin acyltransferase or simply ACAT) is an intracellular protein located in the endoplasmic reticulum that forms cholesteryl esters from cholesterol.

Sterol O-acyltransferase catalyzes the chemical reaction:

Thus, the two substrates of this enzyme are acyl-CoA and cholesterol, whereas its two products are CoA and cholesteryl ester.

This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups, the membrane-bound O-acyltransferases. This enzyme participates in bile acid biosynthesis.

Acyl-CoA cholesterol acyl transferase EC 2.3.1.26, more simply referred to as ACAT, also known as sterol O-acyltransferase (SOAT), belongs to the class of enzymes known as acyltransferases. The role of this enzyme is to transfer fatty acyl groups from one molecule to another. ACAT is an important enzyme in bile acid biosynthesis.

In nearly all mammalian cells, ACAT catalyzes the intracellular esterification of cholesterol and formation of cholesteryl esters. The esterification of cholesterol mediated by ACAT is functionally significant for several reasons. ACAT-mediated esterification of cholesterol limits its solubility in the cell membrane lipids and thus promotes accumulation of cholesterol ester in the fat droplets within cytoplasm; this process is important because the toxic accumulation of free cholesterol in various cell membrane fractions is prevented. Most of the cholesterol absorbed during intestinal transport undergoes ACAT-mediated esterification before incorporation in chylomicrons. In the liver, ACAT-mediated esterification of cholesterol is involved in the production and release of apoB-containing lipoproteins. ACAT also plays an important role in foam cell formation and atherosclerosis by participating in accumulating cholesterol esters in macrophages and vascular tissue. The rate-controlling enzyme in cholesterol catabolism, hepatic cholesterol 7-hydroxylase, is believed to be regulated partly by ACAT.

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