title: Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation.
abstract: The valorization of aromatic heteropolymer lignin is an important unsolved problem in the development of a biomass-based biorefinery, for which novel high-activity biocatalysts are needed. Sequencing of the genomic DNA of lignin-degrading bacterial strain Sphingobacterium sp. T2 revealed no matches to known lignin-degrading genes. Proteomic matches for two manganese superoxide dismutase proteins were found in partially purified extracellular fractions. Recombinant MnSOD1 and MnSOD2 were both found to show high activity for oxidation of Organosolv and Kraft lignin, and lignin model compounds, generating multiple oxidation products. Structure determination revealed that the products result from aryl-Cα and Cα-Cβ bond oxidative cleavage and O-demethylation. The crystal structure of MnSOD1 was determined to 1.35 Å resolution, revealing a typical MnSOD homodimer harboring a five-coordinate trigonal bipyramidal Mn(II) center ligated by three His, one Asp, and a water/hydroxide in each active site. We propose that the lignin oxidation reactivity of these enzymes is due to the production of a hydroxyl radical, a highly reactive oxidant. This is the first demonstration that MnSOD is a microbial lignin-oxidizing enzyme.
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Goran M M
authors.initials: GM
authors.lastname: Rashid
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Taylor
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Yangqingxue
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Dean
authors.initials: D
authors.lastname: Rea
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Vilmos
authors.initials: V
authors.lastname: Fülöp
authors.affiliation: Department of Chemistry and ‡School of Life Sciences, University of Warwick , Coventry CV4 7AL, United Kingdom.
authors.forename: Timothy D H
authors.initials: TD
authors.lastname: Bugg
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D008954:Models, Biological; D015394:Molecular Structure; D010084:Oxidation-Reduction; D040901:Proteomics; D016415:Sequence Alignment; D045249:Sphingobacterium / Q000201:enzymology*; D013482:Superoxide Dismutase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000099156:Superoxide Dismutase 2
chemical_list: D008031:Lignin; D008345:Manganese; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2