Structural and Electronic Modulations of Lytic Polysaccharide Monooxygenase (LPMO) upon Chitin Binding: Insights from X-ray Spectroscopy

Lytic polysaccharide monooxygenases (LPMOs) play a critical role in the depolymerization of recalcitrant polysaccharides, such as chitin, making them of interest in biotechnological applications. This report investigates the structural and electronic changes at the copper (Cu) site of the SmAA10A LPMO upon binding with chitin, utilizing a suite of spectroscopic and computational methods. Herein, we present the first reported X-ray Absorption (XAS) and Emission (XES) spectroscopic data on substrate-bound LPMO. By comparing the Cu(II) and Cu(I) states of SmAA10A in both the chitin-bound and unbound states, we provide insights into the structural adjustments facilitating substrate specificity and the productive catalytic turnover of the enzyme. Our results indicate a binding-induced conformational change in Cu(I) site geometry and concurrent modulations to the electronic structure, which prime the enzyme for targeted C–H activation. This work offers an atomistic understanding of interaction dynamics between the LPMO Cu site and the chitin substrate, advancing our knowledge of LPMO functionality and substrate specificity.