Acetoacetyl-CoA thiolase(ACAT1) is an enzyme member of the membrane-bound acyltransferase family and Sterol o-acyltransferase subfamily. The ACAT1 enzyme catalyzes the reversible formation of acetoacetyl-CoA from 2 molecules of acetyl-CoA. ACAT1 plays a part in lipoprotein compilation and dietary cholesterol absorption. Added to its acyltransferase activity, ACAT1 acts as a ligase.