Mimicking the Reactivity of LPMOs with a Mononuclear Cu Complex.

Lytic polysaccharide monooxygenases (LPMOs) are Cu-dependent metalloenzymes that catalyze the hydroxylation of strong C-H bonds in polysaccharides using O or HO as oxidants (monooxygenase/peroxygenase). In the absence of C-H substrate, LPMOs reduce O to HO (oxidase) and HO to HO (peroxidase) using proton/electron donors. This rich oxidative reactivity is promoted by a mononuclear Cu center in which some of the amino acid residues surrounding the metal might can accept and donate protons and/or electrons during O and HO reduction. Herein, we utilize a podal ligand containing H-bond/proton donors (LH) to analyze the reactivity of mononuclear Cu species towards O and HO. [(LH)Cu] (), [(LH)Cu] (), [(LH)Cu] (), [(LH)Cu(OH)] (), and [(LH)Cu(OOH)] () were synthesized and characterized by structural and spectroscopic means. Complex reacts with O to produce , which releases HO to generate , suggesting that O is used by LPMOs to generate HO. The reaction of with HO produces and hydroxyl radical, which reacts with C-H substrates in a Fenton-like fashion. Complex , which generate via a reversible protonation/reduction, binds HO and HO to produce and , respectively, a mechanism that could be used by LPMOs to control oxidative reactivity.