Structural domains comprising this superfamily share the structure of domain 1 of choline/carnitine o-acyltransferase, two evolutionary and structurally related enzymes. These are two different types of acyltransferases, a type of transferase enzymes that transfer an acetyl group. The former, choline O-acyltransferase, is involved choline biosynthesis and it is essential for the development and neuronal activities of cholinergic systems involved in many fundamental brain functions PMID:15477102. The latter, carnitine o-acyltransferase, catalyzes the reversible acylation of L-carnitine and thus plays a vital role in fatty acid beta-oxidation and maintenance of acyl coenzyme A (acyl-CoA) pools PMID:8420957. Both show a remarkably similar structure, they are monomeric proteins containing two domains (1 and 2) that interconnect to form an active site tunnel PMID:15477102.