Fig. 2.

Superoxo mechanism for polysaccharide hydroxylation by a fungal LPMO. (A) Proposed oxidative mechanism with a Cu(II)-superoxo ([Cu(II)]-O-O⋅) ROS for C1 hydroxylation. C4 hydroxylation results are shown in SI Appendix, Fig. S4. Intermediates and TSs (‡) are shown for each geometry considered. Three enzyme–substrate configurations were considered for both C1 and C4 hydroxylation (SI Appendix, Table S3). (B) Potential energy surface for C1 hydroxylation. Energies in kcal/mol. (C) B3LYP/6–31G(d) optimized structures of intermediates and TSs for the Cu(II)-superoxo ROS mechanism.