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. ISSN 0006-2960

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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
Subjects:	Q Science > QP Physiology
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Lignin -- Biodegradation, Peroxidase
Journal or Publication Title:	Biochemistry
Publisher:	American Chemical Society
ISSN:	0006-2960
Date:	2011
Volume:	Vol.50
Number:	No.23
Page Range:	pp. 5108-5119
Identification Number:	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)
URI:	http://wrap.warwick.ac.uk/id/eprint/40289

Data sourced from Thomson Reuters' Web of Knowledge

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