Lytic polysaccharide monooxygenases (LPMOs): A double-edged sword in biomass polysaccharide degradation

The discovery of lytic polysaccharide monooxygenases (LPMOs) has introduced a novel mechanism for polysaccharide depolymerization, revolutionizing the traditional understanding of biomass degradation. As a class of copper ion-dependent oxidoreductase, LPMOs increase substrate accessibility for glycoside hydrolases (GHs) by oxidatively cleaving glycosidic bonds in crystalline polysaccharides, thereby enhancing overall degradation efficiency. Despite their well-recognized benefits, the unique catalytic mechanism of LPMOs presents significant challenges, including the generation of complex product profiles and susceptibility to self-oxidative inactivation, which currently limit their broader industrial application. This review provides a comprehensive overview of the catalytic mechanism of LPMOs, the diversity of their products, analytical techniques for product identification, and the intricate interactions (synergistic and inhibitory) between LPMOs and GHs during biomass degradation. Particular emphasis is placed on the key differences between the products generated by LPMOs and endoglucanase, as well as the underlying factors that trigger inhibitory effects. Current challenges were further discussed and prospective research directions were outlined. A deeper insight into the functions of LPMOs, and their interactions with GHs is essential for the development of more efficient biomass degradation systems.