Sterol O-acyltransferase 1 (SOAT1), also known as ACAT1, catalyzes the formation of intracellular cholesterol esters in various tissues, such as adult human liver, adrenal glands, macrophages, and kidneys. Specifically, ACAT-1 catalyzes the reversible reaction forming acetoacetyl-CoA from two molecules of acetyl-CoA. Additionaly, the ACAT 1 protein may have a role in lipoprotein assembly and dietary cholesterol absorption, and may also act as a ligase.
Mutations in this gene have been associated with 3-ketothiolase deficiency, an inborn defect of isoleucine catabolism characterized by urinary excretion of 2-methyl-3-hydroxybutyric acid, 2-methylacetoacetic acid, tiglylglycine, and butanone.