All calculations are based on a previously equilibrated and optimized structure 37 of the resting state of the LPMO-substrate complex from Lentinus similis Structure optimizations and energy calculations were performed with the QM software Turbomole (version 7.4) and the MM software AMBER 22 using the program ComQum to combine QM and MM programs. MM calculations employed the Amber protein force field ff14SB. The MM part is kept fixed during all calculations. Structure optimizations were performed using the dispersion corrected TPSS-D3 functional with Becke-Johnson damping and the def2-SV(P) basis set. Calculations with the TPSS functional were always carried out employing the resolution of identity (RI) approximation with the corresponding standard auxiliary basis set. All species with an even number of electrons were calculated in both the singlet and triplet (tr) states. The singlets were in most cases calculated with an (broken-symmetry) open-shell (os) formalism, although in a few cases a spin-restricted closed-shell (cs) formalism was employed. The employed formalism is always explicitly written. The triplet and open-shell singlet calculations employed spin-unrestricted formulations. The best convergence to open-shell singlet states was obtained if the calculations were initiated from the triplet structures (optimized employing TPSS/def2-SV(P)).