The interplay between lytic polysaccharide monooxygenases and glycoside hydrolases

In nature, enzymatic degradation of recalcitrant polysaccharides such as chitin and cellulose takes place by a synergistic interaction between glycoside hydrolases (GHs) and lytic polysaccharide monooxygenases (LPMOs). The two different families of carbohydrate-active enzymes use two different mechanisms when breaking glycosidic bonds between sugar moieties. GHs employ a hydrolytic activity and LPMOs are oxida-tive. Consequently, the topologies of the active sites differ dramatically. GHs have tunnels or clefts lined with a sheet of aromatic amino acid residues accommodating single polymer chains being threaded into the active site. LPMOs are adapted to bind to the flat crystalline surfaces of chitin and cellulose. It is believed that the LPMO oxidative mechanism provides new chain ends that the GHs can attach to and degrade, often in a processive manner. In-deed, there are many reports of synergies as well as rate enhancements when LPMOs are applied in concert with GHs. Still, these enhancements vary in magnitude with respect to the nature of the GH and the LPMO. Moreover, impediment of GH catalysis is also observed. In the present review, we discuss central works where the interplay between LPMOs and GHs has been studied and comment on future challenges to be addressed to fully use the potential of this interplay to improve enzymatic polysaccharide degradation.

Automated summary

In nature, the enzymatic degradation of recalcitrant polysaccharides involves the collaborative action of glycoside hydrolases (GHs) and lytic polysaccharide monooxygenases (LPMOs) through different mechanisms. GHs use a hydrolytic approach, while LPMOs are oxidative. The interplay between LPMOs and GHs can provide rate enhancements and improved degradation of polysaccharides, although the exact magnitude of the enhancements depends on the nature of the specific GH and LPMO. The understanding of this interplay is important for enhancing enzymatic polysaccharide degradation.