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Characterization of a bacterial copper‐dependent lytic polysaccharide monooxygenase with an unusual second coordination sphere
Author(s) -
Munzone Alessia,
El Kerdi Bilal,
Fanuel Mathieu,
Rogniaux Hélène,
Ropartz David,
Réglier Marius,
Royant Antoine,
Simaan A. Jalila,
Decroos Christophe
Publication year - 2020
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.15203
Subject(s) - glycosidic bond , active site , chitin , polysaccharide , biology , stereochemistry , chemistry , biochemistry , enzyme , chitosan
Lytic polysaccharide monooxygenases ( LPMO s) are copper‐dependent enzymes involved in the degradation of recalcitrant polysaccharides such as cellulose or chitin. LPMO s act in synergy with glycoside hydrolases such as cellulases and chitinases by oxidatively cleaving a number of glycosidic bonds at the surface of their crystalline substrate(s). Besides their role in biomass degradation, some bacterial LPMO s have been found to be virulence factors in some human and insect pathogens. Photorhabdus luminescens is a nematode symbiont bacterium that is pathogenic to a wide range of insects. A single gene encoding a LPMO is found in its genome. In this work, we report the characterization of this LPMO , referred to as Pl AA 10. Surprisingly, Pl AA 10 lacks the conserved alanine residue (substituted by an isoleucine) found in the second coordination sphere of the copper‐active site in bacterial LPMO s. Pl AA 10 was found to be catalytically active on both α‐ and β‐chitin, and exhibits a C1‐oxidation regiospecificity, similarly to other chitin‐active LPMO s. The 1.6 Å X‐ray crystal structure confirmed that Pl AA 10 adopts the canonical immunoglobulin‐like fold typical for LPMO s. The geometry of the copper‐active site is not affected by the nearby isoleucine, as also supported by electron paramagnetic resonance. Nevertheless, the bulkier side chain of isoleucine protrudes from the substrate‐binding surface. A bioinformatic study on putative bacterial LPMO s unveiled that they exhibit some variability at the conserved active‐site alanine position with a substitution in about 15% of all sequences analyzed. Database Structural data (atomic coordinates and structure factors) reported for Pl AA 10 are available in the Protein Data Bank under accession number 6T5Z . Enzymes Pl AA10, EC1.14.99.53 .