Brivio, Michela, Schlosrich, Janne, Ahmad, Mark, Tolond, Caroline and Bugg, Tim. (2009) Investigation of acid-base catalysis in the extradiol and intradiol catechol dioxygenase reactions using a broad specificity mutant enzyme and model chemistry. Organic & Biomolecular Chemistry, Vol.7 (No.7). pp. 1368-1373. ISSN 1477-0520

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Abstract

The extradiol and intradiol catechol dioxygenase reaction mechanisms proceed via a common proximal hydroperoxide intermediate, which is processed via different Criegee 1,2-rearrangements. An R215W mutant of extradiol dioxygenase MhpB, able to produce a mixture of extradiol and intradiol cleavage products, was analysed at pH 5.2-8.6, and the yield of extradiol product was found to be highly pH-dependent, whereas the yield of intradiol product was pH-independent. The acid-base chemistry of a biomimetic reaction for extradiol oxidative catechol cleavage was also investigated, using 1,4,7-triazacyclononane, FeCl2, and pyridine in methanol, in which pyridine is proposed to act as both a general base and (in protonated form) a general acid. Kinetic experiments using a range of meta-and para-substituted pyridines gave a Bronsted plot of log(v) vs. pK(a) showing a bell-shaped plot. Oxidative catechol cleavage by a pyridine-monosubstituted beta-cyclodextrin in the presence of TACN and FeCl2 in methanol yielded only intradiol cleavage products. It is therefore proposed that bifunctional acid-base catalysis is required for iron (II)-dependent extradiol catechol cleavage, whereas the rate-determining step for intradiol catechol cleavage does not involve acid-base catalysis.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QP Physiology
Divisions:	Other > Institute of Advanced Study Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Acid-base chemistry, Metalloenzymes, Catechol, Escherichia coli
Journal or Publication Title:	Organic & Biomolecular Chemistry
Publisher:	Royal Society of Chemistry
ISSN:	1477-0520
Date:	2009
Volume:	Vol.7
Number:	No.7
Number of Pages:	6
Page Range:	pp. 1368-1373
Identification Number:	10.1039/b821559f
Status:	Peer Reviewed
Publication Status:	Published
Funder:	Erasmus Mundus (Program)
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URI:	http://wrap.warwick.ac.uk/id/eprint/28271

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