P37: Catalytic promiscuity in tyrosinase for lignin degradation

Recent concerns about the depletion of fossil fuels and climate changes lead research interests and efforts towards the development of the biorefinery system producing biofuels or biochemicals from renewable biomass. Especially, lignocellulosic biomass received attention as the substrates for the fermentation because it is most abundant and does not compete with food chains. In order to use lignocellulosic biomass efficiently as a feedstock, the degradation of lignin must be preceded in prior to convert cellulose and hemicellulose to fermentable sugars which microbe utilize for valuable chemical production. However, already-known-lignin degrading biocatalysts have been limited to apply large scale biorefinery system due to the drawbacks such as a low activity, a poor stability, etc. Herein, we discover a novel catalytic promiscuity, which is the ability to catalyze different types of chemical transformation, in tyrosinase (E.C. 1.14.18.1) in order to overcome the limitations in already known lignin degrading biocatalysts. The novel catalytic promiscuity in tyrosinase was investigated using lignin monomer and dimer model compounds as the substrates, the catalytic products were identified GC/MS, and the catalytic mechanism about the promiscuity was proposed based on the flexible docking simulation.