Light‐driven Lytic Polysaccharide Monooxygenase Catalysis Mediated by Type I Photosensitizers

Abstract

The use of light as abundant, renewable, and clean energy source to boost lytic polysaccharide monooxygenase (LPMO) reactions represents an exciting and yet under‐explored opportunity. Herein we demonstrated that photosensitizers, commonly used in photodynamic therapy, which act through the photocatalytic Type I mechanism can drive the oxidation of PASC by LPMOs, whereas Type II photosensitizers are not capable of promoting the LPMO activity. We analyzed Type I and Type II photosensitizers (methylene blue and tetraiodide salt of meso‐tetrakis‐(4‐N‐methylpyridyl) porphyrin, respectively) and demonstrated that, even without an addition of external reductant, Type I was capable of boosting Thermothelomyces thermophila MtLPMO9A activity in the presence of light. We also evaluated the photobiosystem in the presence and/or absence of molecular oxygen (O2) and hydrogen peroxide (H2O2), and investigated the role of superoxide radical in the methylene blue fueled reactions. Furthermore, we demonstrated that sodium bisulfite (NaHSO3), a chemical scavenger of H2O2, acts by safeguarding the enzyme from oxidative damage caused by accumulation of H2O2 early in photosensitizer‐driven LPMO reactions. Finally, the results of the present work demonstrated that light‐driven LPMO reactions mediated photodynamic therapy (PDT) Type I photosensitizers, which also includes molecules such as curcumin and riboflavin, is a general phenomenon.