Structural and functional characterization of a small chitin‐active lytic polysaccharide monooxygenase domain of a multi‐modular chitinase from Jonesia denitrificans

Lytic polysaccharide monooxygenases (LPMOs) boost enzymatic depolymerization of recalcitrant polysaccharides, such as chitin and cellulose. We have studied a chitin‐active LPMO domain (JdLPMO10A) that is considerably smaller (15.5 kDa) than all structurally characterized LPMOs so far and that is part of a modular protein containing a GH18 chitinase. The 1.55 Å resolution structure revealed deletions of interacting loops that protrude from the core β‐sandwich scaffold in larger LPMO10s. Despite these deletions, the enzyme is active on alpha‐ and beta‐chitin, and the chitin‐binding surface previously described for larger LPMOs is fully conserved. JdLPMO10A may represent a minimal scaffold needed to catalyse the powerful LPMO reaction.