The discovery and enzymatic characterization of a novel AA10 LPMO from Bacillus amyloliquefaciens with dual substrate specificity

Abstract

Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes, which can catalyze the oxidative cleavage of polysaccharide β-1,4 glycosidic bonds to improve the hydrolysis efficiency of the substrate by other glycoside hydrolases. To improve the conversion efficiency of cellulose and chitin, a strain was screened from the soil of Yuelu Mountain in Hunan province, China. The gene sequence of a novel AA10 LPMO (BaLPMO10) was successfully cloned from the genome of the strain and heterologously expressed in E. coli BL21 (DE3). The optimal enzyme activity of BaLPMO10 was observed at pH 6.0 and 70 °C using 2,6-dimethoxyphenol as substrate, and its maximum specific activity was 91.4 U/g. When BaLPMO10 synergized with glycoside hydrolase to degrade microcrystalline cellulose and colloidal chitin, the reducing sugar content increased by 7% and 23%, respectively, compared to glycoside hydrolase alone. Moreover, the results of molecular docking and molecular dynamics simulation showed that the distance between BaLPMO10 and cellohexaose were further than that of BaLPMO10 and chitohexaose, and the number of hydrogen bonds between BaLPMO10 and cellohexaose were lower than that of BaLPMO10 and chitohexaose. Finally, the hot spot residues of BaLPMO10 interacting with chitohexaose/cellohexaose were identified.

Keywords: Enzymatic properties; Heterologous expression; Lytic polysaccharide monooxygenase; Molecular dynamics simulation; Strain screening; Synergistic action.