Correlating Experiment and Theory for Electron Paramagnetic Resonance and Substrate Binding in a Lytic Polysaccharide Monooxygenase

Lytic polysaccharide monooxygenases (LPMOs) are enzymes that binds polysaccharides followed by an (oxidative) disruption of the polysaccharide surface, thereby boosting depolymerization. The binding process between LPMO and polysaccharide is key to the mechanism and recent investigations have established structure-function relationships for this binding, employing hyperfine coupling constants (HFCs) from EPR spectroscopy. Unfortunately, EPR does not provide direct structural data and therefore the experimental EPR parameters have been supported with parameters cal-

culated with density functional theory. Yet, calculated HFCs are extremely sensitive

to the employed computational setup. Using the LPMO Ls(AA9)A, we here quantify

the importance of several choices in the computational setup, ranging from the use

of specialized basis, the underlying structures, and the employed exchange–correlation

functional. We compare our results to both X-ray structures and experiment (EPR spectra) for Ls(AA9)A as well as to recent experimental/theoretical results for another

(AA10) family of LPMOs.