A lytic polysaccharide monooxygenase from Myceliophthora thermophila C1 and its characterization in cleavage of glycosidic chain of cellulose

Lytic polysaccharide monooxygenase (LPMO), a kind of copper-dependent oxidases, has been widely used for the efficient enzymatic hydrolysis of lignocellulosic biomass. In this study, a gene encoding the LPMO from Myceliophthora thermophila Cl (MtC1LPMO) was expressed in Pichia pastoris GS115. A high secretion level of recombinant MtC1LPMO protein was obtained in the culture medium using its native signal peptide. Consequently, MtC1LPMO with a purity of more than 95 % and yield of 46 mg/L was obtained. The optimal enzyme activity was observed at pH 7.5 and 85 degrees C, and the enzyme displayed remarkable thermostability at 40-60 degrees C. MtC1LPMO exhibited a synergistic activity with cellulase in the degradation of microcrystalline cellulose, and the reducing sugar content increased by 290/0 compared to cellulase alone. Additionally, the results of scanning electron microscopy revealed that MtC1LPMO would cleave the glycosidic chain, leading to subsequent disruption to the surface of microcrystalline cellulose. Finally, the interaction model of MtC1LPMO and cellohexaose was explored using molecular docking simulations, which showed that the residues H1, H68, Y153, H142, Y67, V143, 5146, G149, Q151 and P69 of MtC1LPMO played an important role in interacting with cellohexaose.