Inactivating effect of phenolic unit structures on the biodegradation of lignin by lignin peroxidase from Phanerochaete chrysosporium

• Degradation of lignin dimers was performed by a recombinant lignin peroxidase LiP H8.
• The free-phenolic group of lignin inhibited LiP to prevent further degradation of lignin.
• Free phenolic group strongly interacts with surface active site of LiP.

An imbalance of electron in an intramolecular electron transfer pathway was identified as the central factor causing inefficient degradation of lignin by the lignin peroxidase H8 from Phanerochaete chrysosporium (LiPH8). It was elucidated that dimeric lignins or monolignolic analogs containing free-hydroxyl phenolic groups were not only favorable substrates for the reduction of LiPH8 but also strong inhibitors depressing the enzymatic degradation of lignin. The data collectively demonstrated that disturbing the interaction between the free OH group on the phenolic structure and the surface active sites around Trp171 caused the primary deficiency in electron transport between Trp171 and the heme site, which severely inhibited the efficiency of lignin biodegradation by LiPH8/H2O2.