title: Improved manganese-oxidizing activity of DypB, a peroxidase from a lignolytic bacterium.
abstract: DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn(2+)), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme's apparent k(cat) and k(cat)/K(m) values for Mn(2+) by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn(2+) to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn(2+)-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant's high K(m) for Mn(2+) (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Rahul
authors.initials: R
authors.lastname: Singh
authors.forename: Jason C
authors.initials: JC
authors.lastname: Grigg
authors.forename: Wei
authors.initials: W
authors.lastname: Qin
authors.forename: John F
authors.initials: JF
authors.lastname: Kadla
authors.forename: Michael E P
authors.initials: ME
authors.lastname: Murphy
authors.forename: Lindsay D
authors.initials: LD
authors.lastname: Eltis
mesh_terms: D001419:Bacteria / Q000201:enzymology*; D001665:Binding Sites; D055162:Biocatalysis; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D006868:Hydrolysis; D008031:Lignin / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008345:Manganese; D008031:Lignin; D010544:Peroxidases