Reductant-independent oxidative cleavage of cellulose by a novel marine fungal lytic polysaccharide monooxygenase.

Among the enzymes derived from fungus that act on polysaccharides, lytic polysaccharide monooxygenase (LPMOs) has emerged as a new member with complex reaction mechanisms and high efficiency in dealing with recalcitrant crystalline polysaccharides. This study reported the characteristics, structure, and biochemical properties of a novel LPMO from Talaromyces sedimenticola (namely MaLPMO9K) obtained from the Mariana Trench. MaLPMO9K was a multi-domain protein combined with main body and a carbohydrate-binding module. It was heterologously expressed in E. coli for analyzing peroxidase activity in reactions with the substrate 2,6-DMP, where HO serves as a co-substrate. Optimal peroxidase activity for MaLPMO9K was observed at pH 8 and 25 °C, achieving the best V value of 265.2 U·g. In addition, MaLPMO9K also demonstrated the ability to treat cellulose derivatives, and cellobiose substrates without the presence of reducing agents.