 Animal ACL enzymes are homomeric; a fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.The mammalian ATP citrate lyase has a N-terminal citrate-binding domain that adopts a Rossmann fold, followed by a CoA binding domain and CoA-ligase domain and finally a C-terminal citrate synthase domain.The cleft between the CoA binding and citrate synthase domains forms the active site of the enzyme, where both citrate and acetyl-coenzyme A bind.