A novel mechanism for azoreduction

Ali Ryan, Nicola Laurieri, Isaac Westwood, Chan Ju Wang, Edward Lowe, Edith Sim*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)24-37
Number of pages14
JournalJournal of Molecular Biology
Issue number1
Publication statusPublished - Jul 2010
Externally publishedYes


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