Manganese, Mn-dependent peroxidases, and the biodegradation of lignin

Manganese and Mn-dependent peroxidases have been implicated in the enzymatic degradation of lignin. However, the specific role of manganese is uncertain. We report here the novel observation that in the absence of enzyme, suitably chelated Mn3+ is a ligninolytic agent capable of oxidizing veratryl alcohol, lignin model compounds, and lignin. We also demonstrate the unexpected effect of reducing agents which stimulate the oxidations by Mn3+. The stimulation is apparently through the production of a reduced oxygen species likely to be superoxide. These observations provide a fresh insight into the process of lignin biodegradation.