Mimicking the Cu Active Site of Lytic Polysaccharide Monooxygenase Using Monoanionic Tridentate N-Donor Ligands

Abstract

In an effort to prepare small molecule mimics of the active site of lytic polysaccharide monooxygenase (LPMO), three monoanionic tridentate N donor ligands comprising a central deprotonated amide group flanked by two neutral donors were prepared, and their coordination chemistry with Cu(I) and Cu(II) was evaluated. With Cu(I), a dimer formed, which was characterized by X-ray crystallography and NMR spectroscopy. A variety of mononuclear and dinuclear Cu(II) species with a range of auxiliary ligands (MeCN, Cl – , OH – , OAc – , OBz – , CO 3 2– ) were prepared and characterized by X-ray diffraction and various spectroscopies (UV–vis, EPR). The complexes exhibit structural similarities to the LPMO active site.

LPMO‐like Activity of Bioinspired Copper Complexes: From Model Substrate to Extended Polysaccharides

“…Since these first reports, several complexes modelling the coordination sphere of LPMO were prepared using conventional N ‐based ligands (pyridines, (benz)imidazoles, amines) [31–37] . or amino acid/peptide‐based ligands to reproduce the primary amine ligation found in the enzymatic system [38–40] .…”

“…[30] Since these first reports, several complexes modelling the coordination sphere of LPMO were prepared using conventional N-based ligands (pyridines, (benz)imidazoles, amines). [31][32][33][34][35][36][37] or amino acid/peptide-based ligands to reproduce the primary amine ligation found in the enzymatic system. [38][39][40] A variety of substrates were used to evaluate their activity ranging from simple benzyl alcohol [38] to soluble substrates (p-NPG, [31,32,37,39] cellobiose, [35] p-NP-glycosidic substrates) [33] and one report on the use of insoluble cellulosic substrate.…”

A designed Copper Histidine-brace enzyme for oxidative depolymerization of polysaccharides as a model of lytic polysaccharide monooxygenase

“…Due to the general scarcity of proteins containing His-brace sites and the lack of catalytic activity in natural non-LPMO His-brace-containing proteins, the design of artificial models containing the His-brace site would provide insight into the structure–function relationship of His-brace and LPMO and expand our understanding of this class of metalloproteins for other activities. Toward this goal, several Cu-organometallic complexes have been reported as mimics of His-brace and LPMO ( 46 – 55 ). For example, a biotin-modified Cu complex has been incorporated into streptavidin, which shows Cu-bound H 2 O 2 stabilized by the local protein environment in the X-ray crystal structure ( 56 ).…”