In 2010, it was shown that proteins previously known as chitin-binding proteins or carbohydrate-binding modules of family 33 (CBM33) and, by analogy, proteins previously classified as glycoside hydrolases of family 61 (GH61), catalyse oxidative cleavage of glycosidic bonds. The discovery of these enzymes, today called lytic polysaccharide monooxygenases (LPMOs), has revolutionized our views on enzymatic processing of polysaccharides, in Nature and industry alike. LPMOs are mono-copper enzymes with intriguing and unprecedented catalytic properties, including a unique ability to break glycoside bonds in crystalline substrates. LPMOs require reducing equivalents and an oxygen-containing co-substrate, which was originally thought to be O₂. Recent studies indicate that LPMOs may in fact be peroxygenases, as H₂O₂-driven LPMO reactions are orders of magnitude faster than O₂-driven reactions . It has also become clear that LPMOs suffer from auto-catalytic inactivation if there is a misbalance between available carbohydrate substrate, reducing power and the oxygen-containing co-substrate. These recent findings shed new light on industrial biomass processing  and on the interplay between LPMOs and other oxidoreductases in biomass degrading eco-systems . In this presentation, I will summarize the most recent findings regarding LPMO functionality and discuss knowns and unknowns in the LPMO field [4-6]. Of note, current data indicate that these ubiquitous enzymes may have additional roles, e.g. in microbial pathogenesis, and that their true industrial potential has not yet been harnessed.
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