A fungal metabolite mediates degradation of non‐phenolic lignin structures and synthetic lignin by laccase

Abstract

Lignin peroxidase is generally considered to be a primary catalyst for oxidative depolymerization of lignin by white‐rot fungi. However, some white‐rot fungi lack lignin peroxidase. Instead, many produce laccase, even though the redox potentials of known laccases are two to directly oxidize non‐phenolic components of lignin. Pycnoporus cinnabarinus is one example of a laccase‐producing fungus that degrades lignin very efficiently. To overcome the redox potential barrier, P. cinnabarinus produces a metabolite, 3‐hydroxyanthranilate that can mediate the oxidation of non‐phenolic substrates by laccase. This is the first description of how laccase might function in a biological system for the complete depolymerization of lignin.