Figure 1. Toluene degradation pathway. The initial reaction of anaerobic toluene degradation involves the addition of fumarate to the methyl group. The resulting benzylsuccinate is activated with CoA, after which it is reduced to phenylitaconyl-CoA. This intermediate then undergoes a series of reactions analogous to β-oxidation to benzozyl-CoA. Figure adapted from Biegert et al. (1996).