Structural and functional study of a novel lytic polysaccharide monooxygenase cPMO2 from compost sample in the oxidative degradation of cellulose

Lytic polysaccharide monooxygenases (LPMOs) are the major groups of oxidizing the recalcitrant polysaccharides. Here, a novel AA9 family protein cPMO2 originated from composting was characterized, and it had a better binding capacity to phosphoric acid swollen cellulose (PASC) and Avicel, as well the isothermal titration calorimetry (ITC) analysis showed that it owned a considerable capacity of binding Cu2+ with the K-d value of 1.58 & PLUSMN; 0.78 mu M. Interestingly, the kinetics of cPMO2 by using 2, 6-dimethoxyphenol (2, 6-DMP) as substrate indicated that cPMO2 was a novel member of LPMOs family, with the V-max of 21.30 & PLUSMN; 0.83 U.g(-1) at pH 7.5. In addition, cPMO2 owned a broad substrate specificity, which could act on PASC and xylan at the C1 site based on the MALDI-TOF-MS analysis results. Simultaneously, cPMO2 could also act on Avicel directly resulting the decrease of crystallinity by 4% and further to synergistic degradation of corncob and rice straw with glycoside hydrolases. The structure of the functional region of cPMO2 was obtained by using single-crystal X-ray diffraction, and the enzymatic properties and molecular docking analysis results showed that His1 and Tyr175 were the critical active sites of the cPMO2. Altogether, this study will be a supplement for the AA9 LPMOs in cellulose degradation.