Epoxy coenzyme a thioester pathways for degradation of aromatic compounds

Abstract

Aromatic compounds (biogenic and anthropogenic) are abundant in the biosphere. Some of them are well-known environmental pollutants. Although the aromatic nucleus is relatively recalcitrant, microon of aromatic compounds. The adopted degradation pathways depend on the availabilorganisms have developed various catabolic routes that enable complete biodegradatiityof oxygen. Under oxic conditions, microorganisms utilize oxygen as a cosubstrate to activate and cleave the aromatic ring. In contrast, under anoxic conditions, the aromatic compounds are transformed to coenzyme A (CoA) thioesters followed by energyconsuming reduction of the ring. Eventually, the dearomatized ring is opened via a hydrolytic mechanism. Recently, novelcatabolic pathways for the aerobic degradation of aromatic compounds were elucidated that differ significantly from the established catabolic routes. The new pathways were investigated in detail for the aerobic bacterial degradation of benzoate and phenylacetate. In both cases, the pathway is initiated by transforming the substrate to a CoA thioester and all the intermediates are bound by CoA. The subsequent reactions involve epoxidation of the aromatic ring followed by hydrolytic ring cleavage. Here we discuss the novel pathways, with a particular focus on their unique features and occurrence as well as ecological significance. © 2012, American Society for Microbiology.