Abstract
Lytic polysaccharide (mono)oxygenases (LPMOs) perform oxidative cleavage of polysaccharides, and are key enzymes in biomass processing and the global carbon cycle. It has been shown that LPMO reactions may be driven by light, using photosynthetic pigments or photocatalysts, but the mechanism behind this highly attractive catalytic route remains unknown. Here, prompted by the discovery that LPMOs catalyze a peroxygenase reaction more efficiently than a monooxygenase reaction, we revisit these light-driven systems, using an LPMO from Streptomyces coelicolor (ScAA10C) as model cellulolytic enzyme. By using coupled enzymatic assays, we show that H2O2 is produced and necessary for efficient light-driven activity of ScAA10C. Importantly, this activity is achieved without addition of reducing agents and proportional to the light intensity. Overall, the results highlight the importance of controlling fluxes of reactive oxygen species in LPMO reactions and demonstrate the feasibility of light-driven, tunable enzymatic peroxygenation to degrade recalcitrant polysaccharides.
Highlights
To cite this version: Bastien Bissaro, Eirik Kommedal, Asmund K
Among the enzymatic tools are enzymes today known as lytic polysaccharide monooxygenases (LPMOs), which play a major role in biomass conversion by oxidative cleavage and, structural disruption of biopolymers such as chitin[1,2], cellulose[3,4,5], as well as co-polymeric structures made of cellulose and hemicelluloses[6,7,8]
H2O2 levels (Fig. 2f) and accumulation of high levels of H2O2 in the reaction with the Lytic polysaccharide (mono)oxygenases (LPMOs) and substrate (Fig. 2e). These results indicate that the Chl/light system produces large amounts of O2− and that the degree of conversion O2− to H2O2, e.g., by superoxide dismutase (SOD) (Fig. 2d–f), determines both the catalytic rate and the stability of the LPMO
Summary
To cite this version: Bastien Bissaro, Eirik Kommedal, Asmund K. The standard reaction with only AscA produced more oxidized products compared to the reaction with Chl/light-AscA, because the LPMO stayed active for a much longer time (Fig. 2a).
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