ACAT (Acetyl-CoA Acetyltransferase) is an enzyme involved in cholesterol metabolism and fatty acid synthesis, converting acetyl-CoA to acetoacetyl-CoA. The main family members include ACAT1 and ACAT2, which consist of multiple functional domains and are primarily located in the endoplasmic reticulum and mitochondria. ACAT plays a crucial role in regulating cholesterol esterification, lipid storage, and cell membrane stability. The expression of ACAT is tissue-specific, and mutations or dysregulation in its gene are associated with various diseases, including atherosclerosis, neurodegenerative diseases, and lipid metabolism disorders.