In vitro and in silico studies provide evidence of competitive binding displacement of Agaricus bisporus laccase mediated by lignin-derived monomers.

Agaricus bisporus, the commercially grown edible fungus, possesses ligninolytic enzymes like manganese peroxidase and laccase, which break down the lignin component of mushroom substrate/compost containing wheat straw. This study aims to develop an understanding about the effect of phenolic lignin-derived products (LDPs) on the in vitro/in silico activity of laccase enzymes. The treatment of A. bisporus laccase enzyme with wheat straw hydrolysate revealed an inhibitory effect, possibly due to the presence of LDPs. Individual LDPs and their diversity in A. bisporus substrate were identified through Pyro-GC-MS analysis of uncolonised Phase-II compost, and fully colonised Phase-III-55 compost at the end of the crop cycle. Six commercially available pure LDP compounds (acetosyringone, guaiacylacetone, coniferyl alcohol, 3-ethyl-2-hyrdoxy-2-cyclopent-1-one (EHC), coumaran, and vanillic acid) were used during in vitro assays to test their effect on laccase activity. The results showed coniferyl alcohol and guaiacylacetone as strong laccase inhibitors whereas coumaran exhibited a weaker effect. In silico studies demonstrated that the LDPs exhibited moderate binding potentials at the intermolecular level, with binding affinity ranging from -5.8 to -3.8 kcal/mol. The present study expands current understanding of lignocellulose degradation by employing an integrated in silico and in vitro approach to investigate the competitive effects of selected lignin-derived products (LDPs) on laccase activity and to provide insights into the putative interactions between LDPs and Agaricus bisporus laccase. The relevance of this work is further strengthened by the selection of LDPs that are representative of those present in the A. bisporus growth substrate.