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A Novel Mechanism for Azoreduction

DOI: 10.1016/j.jmb.2010.04.023 DOI Help
PMID: 20417637 PMID Help

Authors: Ali Ryan (University of Oxford) , Nicola Laurieri (University of Oxford) , Isaac Westwood (Institute of Cancer Research) , Chan-ju Wang (University of Oxford) , Ed Lowe (University of Oxford) , Edith Sim (Department of Pharmacology, University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Molecular Biology , VOL 400 (1) , PAGES 24-37

State: Published (Approved)
Published: July 2010

Abstract: Azoreductases are important due to their ability to activate anti-inflammatory azo pro-drugs and to detoxify azo dyes. Three genes encoding azoreductases have been identified in Pseudomonas aeruginosa. We describe here a comparison of the three enzymes. The pure recombinant proteins each have a distinct substrate specificity profile against a range of azo substrates. Using the structure of P. aeruginosa azoreductase (paAzoR) 1 and the homology models of paAzoR2 and paAzoR3, we have identified residues important for substrate specificity. We have defined a novel flavin mononucleotide binding cradle, which is a recurrent motif in many flavodoxin-like proteins. A novel structure of paAzoR1 with the azo pro-drug balsalazide bound within the active site was determined by X-ray crystallography and demonstrates that the substrate is present in a hydrazone tautomer conformation. We propose that the structure with balsalazide bound represents an enzyme intermediate and, together with the flavin mononucleotide binding cradle, we propose a novel catalytic mechanism.

Journal Keywords: Azo; Binding; Crystallography; X-Ray; Flavin; Humans; Models; Molecular; Molecular; NADH; NADPH; Oxidation-Reduction; Protein; Pseudomonas; Sequence; Substrate Specificity

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography

Added On: 06/04/2011 14:33

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