Purification and Structural Characterization of the Auxiliary Activity 9 Native Lytic Polysaccharide Monooxygenase from Thermoascus aurantiacus and Identification of Its C1- and C4-Oxidized Reaction Products

Auxiliary activity 9 (AA9) lytic polysaccharide monooxygenases (LPMOs) are copper-dependent oxidoreductases that use O2 or H2O2 to perform oxidative cleavage of cellulose in the presence an electron donor. Combined with cellulases, they can assist a more efficient cellulose. AA9 LPMOs have therefore attracted considerable attention recent years for biotechnological applications. Here, native LPMO (nTaAA9A) from thermophilic fungus Thermoascus aurantiacus was purified and characterized. The enzyme shown be active able cleave xylan produce C1- C4-oxidized products. It also found retain about 84.3, 63.7, 35.3% its after incubation 30 min at 60, 70, 80 °C, respectively, using quantitative determination. structure determined 1.36 Å resolution compared recombinant expressed Aspergillus oryzae. Structural differences glycosylated Asn138 solvent-exposed loops were identified.