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Name Miss Megan Booth
Organization University of Florida Department of Chemistry
Type Poster
Topic Biochemistry / Chem Bio.
Title

HYDROGEN PEROXIDE GENERATION BY BACILLUS SUBTILIS OXALATE DECARBOXYLASE IN THE ABSENCE OF SUBSTRATE

Author(s)

Megan Booth and Alexander Angerhofer

Author Location(s)

Department of Chemistry, University of Florida, Gainesville FL 32611-7200, USA

Abstract

Oxalate decarboxylase (OxDC) from Bacillus subtilis is a bicupin enzyme possessing a Mn ion in each of its two cupin folds. In 99.8% of all turnovers it acts as a decarboxylase by catalyzing the breakdown of oxalate into formate and CO2. However, in 0.2% of turnover events the enzyme redirects its chemistry to oxidase activity and generates hydrogen peroxide as a product. The mechanism for this reaction is believed to involve oxygen binding at one of the two Mn centers and subsequent formation of a superoxide radical intermediate when one of these centers is oxidized from Mn2+ to Mn3+.  The superoxide generated upon oxidation has the potential to convert into hydrogen peroxide.  Current work utilizing the colorimetric ferrous-xylenol orange assay has shown that even without substrate, hydrogen peroxide is still generated at low pH in low concentrations (<1 µM). This suggests that a small percentage of the Mn in the virgin enzyme is already oxidized and produces superoxide before oxalate has even been added.