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Characterization of dye-decolorizing peroxidases from Rhodococcus jostii RHA1
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Roberts, Joseph N., Singh, Rahul, Grigg, Jason C., Murphy, Michael E. P., Bugg, Tim and Eltis, Lindsay D. (2011) Characterization of dye-decolorizing peroxidases from Rhodococcus jostii RHA1. Biochemistry, Vol.50 (No.23). pp. 5108-5119. doi:10.1021/bi200427h ISSN 0006-2960.
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Official URL: http://dx.doi.org/10.1021/bi200427h
Abstract
The soil bacterium Rhodococcus jostii RHA1 contains two dye-decolorizing peroxidases (DyPs) named according to the subfamily they represent: DypA, predicted to be periplasmic, and DypB, implicated in lignin degradation. Steady-state kinetic studies of these enzymes revealed that they have much lower peroxidase activities than C- and D-type DyPs. Nevertheless, DypA showed 6-fold greater apparent specificity for the anthraquinone dye Reactive Blue 4 (kcat/Km = 12800 ± 600 M–1 s–1) than either ABTS or pyrogallol, consistent with previously characterized DyPs. By contrast, DypB showed the greatest apparent specificity for ABTS (kcat/Km = 2000 ± 100 M–1 s–1) and also oxidized MnII (kcat/Km = 25.1 ± 0.1 M–1 s–1). Further differences were detected using electron paramagnetic resonance (EPR) spectroscopy: while both DyPs contained high-spin (S = 5/2) FeIII in the resting state, DypA had a rhombic high-spin signal (gy = 6.32, gx = 5.45, and gz = 1.97) while DypB had a predominantly axial signal (gy = 6.09, gx = 5.45, and gz = 1.99). Moreover, DypA reacted with H2O2 to generate an intermediate with features of compound II (FeIV═O). By contrast, DypB reacted with H2O2 with a second-order rate constant of (1.79 ± 0.06) × 105 M–1 s–1 to generate a relatively stable green-colored intermediate (t1/2 9 min). While the electron absorption spectrum of this intermediate was similar to that of compound I of plant-type peroxidases, its EPR spectrum was more consistent with a poorly coupled protein-based radical than with an [FeIV═O Por•]+ species. The X-ray crystal structure of DypB, determined to 1.4 Å resolution, revealed a hexacoordinated heme iron with histidine and a solvent species occupying axial positions. A solvent channel potentially provides access to the distal face of the heme for H2O2. A shallow pocket exposes heme propionates to the solvent and contains a cluster of acidic residues that potentially bind MnII. Insight into the structure and function of DypB facilitates its engineering for the improved degradation of lignocellulose.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QP Physiology | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
Library of Congress Subject Headings (LCSH): | Lignin -- Biodegradation, Peroxidase | ||||
Journal or Publication Title: | Biochemistry | ||||
Publisher: | American Chemical Society | ||||
ISSN: | 0006-2960 | ||||
Official Date: | 2011 | ||||
Dates: |
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Volume: | Vol.50 | ||||
Number: | No.23 | ||||
Page Range: | pp. 5108-5119 | ||||
DOI: | 10.1021/bi200427h | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Funder: | Natural Sciences and Engineering Research Council Canada (NSERC), Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC) |
Data sourced from Thomson Reuters' Web of Knowledge
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