Structural and functional modelling of LPMO using peptide-copper complexes. – LPMO-PEPS

-The use of lignocellulosic biomass as a renewable source of energy is mainly challenged by its recalcitrance to mechanical and chemical degradation. In LPMO-PEPS, we aim at providing structural and functional models of the Lytic Polysaccharide MonoOxygenases (LPMO), a copper-enzyme able to catalyze the oxidative cleavage of polysaccharides using dioxygen or hydrogen peroxide as oxidants.
-The foreseen bioinspired catalysts are copper peptide (Cu(pep)) complexes. The reasons to use peptide-based scaffolds are multiple: (i) although the copper site in LPMO can be straightforwardly reproduce with peptides, this strategy is still poorly explored in the literature, (ii) in-house preliminary data demonstrate that a first generation of Cu(pep) complexes made with very simple peptide sequences are efficient catalysts for LPMO-like activity, (iii) peptide modifications are straightforward making possible to screen a fairly high number of scaffolds (about 50-100), (iv) peptides are water-soluble making their use in biologically-relevant and environmentally-friendly conditions easy.
-The strength and originality of LPMO-PEPS lie on the unprecedented combined study of LPMO enzymes (wild-type and variants) and model peptides, whose structural and functional characterizations will provide Structure Activity Relationships (SAR). The key structural parameters thus delivered will (i) give important fundamental insights on the enzymatic system and will (ii) serve to optimize future generations of bio-inspired catalysts able to functionalize strong C-H bonds under mild conditions.
-A straightforward methodology is planned with (i) the synthesis of several generations of peptides and enzyme variants, (ii) the selection of the most important structural parameters based on the screening of catalytic activity on model substrates of increasing complexity, including biologically relevant substrates, (iii) the ultimate development of about 10 peptides with optimised features and (iv) the whole structural, functional and mechanistic characterizations of the selected Cu(pep) and LPMOs.
-The structural characterizations will include XAS, EPR, UV-Vis, NMR, electrochemical and DFT studies, including as a function of pH. This will deliver a full picture of the copper-peptide/enzyme interactions from the thermodynamic, kinetic and redox points of view. In addition, the mechanistic investigations will mainly rely on the measurements of reactive oxygen species production by the Cu(pep) and LPMO and on the trapping of oxygenated copper intermediates using spectroscopic methods coupled to freeze-quench and stopped-flow. Altogether, the obtained results will unveil the catalytic mechanism at play of the Cu(pep) complexes from which that of the enzymes will be inferred.