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Structural Features on the Substrate‐Binding Surface of Fungal Lytic Polysaccharide Monooxygenases Determine Their Oxidative Regioselectivity
Author(s) -
Danneels Barbara,
Tanghe Magali,
Desmet Tom
Publication year - 2019
Publication title -
biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.144
H-Index - 84
eISSN - 1860-7314
pISSN - 1860-6768
DOI - 10.1002/biot.201800211
Subject(s) - hypocrea , regioselectivity , neurospora crassa , phanerochaete , monooxygenase , glycosidic bond , chemistry , carbohydrate binding module , biochemistry , stereochemistry , trichoderma reesei , cellulose , enzyme , glycoside hydrolase , cellulase , cytochrome p450 , gene , mutant , catalysis
Lytic polysaccharide monooxygenases (LPMOs) are copper‐dependent enzymes that oxidatively cleave many of nature's most recalcitrant polysaccharides by acting on the C1‐ and/or C4‐carbon of the glycosidic bond. Here, the results of an extensive mutagenesis study on three LPMO representatives, Phanerochaete chrysosporium LPMO9D (C1‐oxidizer), Neurospora crassa LPMO9C (C4), and Hypocrea jecorina LPMO9A (C1/C4), are reported. Using a previously published indicator diagram, the authors demonstrate that several structural determinants of LPMOs play an important role in their oxidative regioselectivity. N‐glycan removal and alterations of the aromatic residues on the substrate‐binding surface are shown to alter C1/C4‐oxidation ratios. Removing the carbohydrate binding module (CBM) is found not to alter the regioselectivity of Hj LPMO9A, although the effect of mutational changes is shown to increase in a CBM‐free context. The accessibility to the solvent‐exposed axial position of the copper‐site reveales not to be a major regioselectivity indicator, at least not in Pc LPMO9D. Interestingly, a Hj LPMO9A variant lacking two surface exposed aromatic residues combines decreased binding capacity with a 22% increase in synergetic efficiency. Similarly to recent LPMO10 findings, our results suggest a complex matrix of surface‐interactions that enables LPMO9s not only to bind their substrate, but also to accurately direct their oxidative force.