What are lytic chitin monooxygenases?

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Lytic chitin monooxygenases belong to the rather new class of lytic polysaccharide monooxygenases (LPMOs), cleaving glycosidic linkages by an oxidative rather than a hydrolytic mechanism. LPMOs have the Enzyme Commission number EC 1.14.99.53; according to the CAZY classification of Carbohydrate Active enZYmes, chitin LPMO belong to the Auxiliary Activity family 10 (AA10) containing copper-dependent LPMOs acting either on chitin or on cellulose. LPMOs typically attack insoluble, crystalline substrates which are difficult to cleave for hydrolytic enzymes. They are thought to generate breaks in the polymer chains on the surface of e.g. a chitin fiber, generating free reducing and non-reducing ends and possibly weakening the crystal structure, thus producing substrates for endo- and exo-acting chitinases for further hydrolytic cleavage. LPMOs had previously been known as substrate (e.g. chitin or cellulose) binding proteins and they had been shown to assist hydrolytic enzymes such as endo-acting chitinases and cellulases, but their catalytic properties have only recently been described, first for the chitin binding protein CBP21 from Serratia marcescens. Note, however, that not all chitin binding proteins are LPMOs.