Aryl-CoA Ligases, subfamily of the adenylate-forming enzyme superfamily

Aryl-CoA ligases belong to class I of the adenylate-forming enzyme superfamily (ANL superfamily) and catalyze the formation of thioester bonds between aromatic compounds and Coenzyme A (CoA) and occur in nearly all forms of life. These ligases are involved in various metabolic pathways degrading benzene, toluene, ethylbenzene, and xylene (BTEX) or polycyclic aromatic hydrocarbons (PAHs). They are often necessary to produce the central intermediate benzoyl-CoA that occurs in various anaerobic pathways. The substrate specificity is very diverse between enzymes within the same class, while the dependency on Mg 2+ , ATP and CoA as well as oxygen insensitivity are characteristics shared by the whole enzyme-class. Some organisms employ the same aryl-CoA ligase when growing aerobically and anaerobically, while others induce different enzymes depending on the environmental conditions. Aryl-CoA ligases can be divided into two major groups, benzoate:CoA ligase-like enzymes and phenylacetate:CoA ligase-like enzymes. They are widely distributed between the phylogenetic clades of the ANL superfamily and show closer relations within the subfamilies than to other aryl-CoA ligases. This, together with residual CoA-ligase activity in various other enzymes of the ANL superfamily, leads to the conclusion that CoA ligases might be the ancestral proteins from which all other ANL superfamily enzymes developed.