A C1/C4-Oxidizing AA10 Lytic Polysaccharide Monooxygenase from Paenibacillus xylaniclasticus Strain TW1.

Lytic polysaccharide monooxygenases (LPMO) are key enzymes for the efficient degradation of lignocellulose biomass with cellulases. A lignocellulose-degradative strain, Paenibacillus xylaniclasticus TW1, has LPMO-encoding PxAA10A gene. Neither the C1/C4-oxidizing selectivity nor the enzyme activity of PxAA10A has ever been characterized. In this study, the C1/C4-oxidizing selectivity of PxAA10A and the boosting effect for cellulose degradation with a cellulase cocktail were investigated. The full-length PxAA10A (rPxAA10A) and the catalytic domain (rPxAA10A-CD) were heterologously expressed in Escherichia coli and purified. To identify the C1/C4-oxidizing selectivity of PxAA10A, cellohexaose was used as a substrate with the use of rPxAA10A-CD, and the products were analyzed by MALDI-TOF/MS. As a result, aldonic acid cellotetraose and cellotetraose, the products from C1-oxidization and C4-oxidization, respectively, were detected. These results indicate that PxAA10A is a C1/C4-oxidizing LPMO. It was also found that the addition of rPxAA10A into a cellulase cocktail enhanced the cellulose-degradation efficiency.