Enhanced in situ H 2 O 2 production explains synergy between an LPMO with a cellulose-binding domain and a single-domain LPMO

Lytic polysaccharide monooxygenases (LPMOs) are mono-copper enzymes that catalyze oxidative depolymerization of recalcitrant substrates such as chitin or cellulose. Recent work has shown that LPMOs catalyze fast peroxygenase reactions and that, under commonly used reaction set-ups, access to in situ generated H 2 O 2 likely limits catalysis. Based on a hypothesis that the impact of a cellulose-binding module (CBM) on LPMO activity could relate to changes in in situ H 2 O 2 production, we have assessed the interplay between CBM-containing Sc LPMO10C and its truncated form comprising the catalytic domain only ( Sc LPMO10C TR ). The results show that truncation of the linker and CBM leads to elevated H 2 O 2 production and decreased enzyme stability. Most interestingly, combining the two enzyme forms yields strong synergistic effects, which are due to the combination of high H 2 O 2 generation by Sc LPMO10C TR and efficient productive use of H 2 O 2 by the full-length enzyme. Thus, cellulose degradation becomes faster, while enzyme inactivation due to off-pathway reactions with excess H 2 O 2 is reduced. These results underpin the complexity of ascorbic acid-driven LPMO reactions and reveal a potential mechanism for how LPMOs may interact synergistically during cellulose degradation.