pH-Dependent Relationship between Catalytic Activity and Hydrogen Peroxide Production Shown via Characterization of a Lytic Polysaccharide Monooxygenase from Gloeophyllum trabeum

Lytic polysaccharide monooxygenases promote enzymatic depolymerization of lignocellulosic materials by microorganisms due to their ability to oxidatively cleave recalcitrant polysaccharides. The properties of these copper-dependent enzymes are currently of high scientific and industrial interest. We describe a previously uncharacterized fungal LPMO and show how reductants, which are needed to prime the LPMO by reducing Cu(II) to Cu(I) and to supply electrons during catalysis, affect enzyme efficiency and stability. The results support claims that H2 O2 is a natural cosubstrate for LPMOs by demonstrating that when certain reductants are used, catalysis can be driven only by H2 O2 and not by O2 . Furthermore, we show how auto-inactivation resulting from endogenous generation of H2 O2 in the LPMO-reductant system may be prevented. Finally, we identified a reductant that leads to enzyme activation without any endogenous H2 O2 generation, allowing for improved control of LPMO reactivity and providing a valuable tool for future LPMO research.