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EPR Monitored Redox Titration of the Cofactors of Saccharomyces cerevisiae Nar1
Published on: November 26, 2014
Reversible biological Birch reduction at an extremely low redox potential
Johannes W Kung1, Sven Baumann, Martin von Bergen
1Institute of Biochemistry, University of Leipzig, 04103 Leipzig, Germany.
Journal of the American Chemical Society
|June 29, 2010
Summary
Researchers discovered a tungsten-containing enzyme that reverses aromatic ring reduction, unlike typical chemical methods. This metalloenzyme catalysis offers a highly efficient, reversible pathway for dearomatization reactions.
Area of Science:
- Biochemistry
- Enzymology
- Organic Chemistry
Background:
- Aromatic ring reduction is crucial in synthesis but often irreversible.
- Benzoyl-coenzyme A (CoA) reductases (BCRs) are key in anaerobic aromatic degradation.
- Class I BCRs use FeS clusters and ATP hydrolysis for dearomatization.
Purpose of the Study:
- Investigate a novel tungsten-containing class II BCR from Geobacter metallireducens.
- Characterize its catalytic mechanism and redox properties.
- Explore its potential for reversible aromatic reduction.
Main Methods:
- Enzyme purification and characterization.
- Redox titration experiments with a low-potential redox dye.
- Analysis of catalytic activity in benzoyl-CoA dearomatization and disproportionation.
Main Results:
- The class II BCR catalyzes ATP-independent, reversible dearomatization of benzoyl-CoA.
- It also mediates disproportionation and multi-electron reduction of benzoyl-CoA.
- The benzoyl-CoA/dienoyl-CoA couple exhibits a very low midpoint potential of -622 mV.
Conclusions:
- Class II BCRs offer a unique, reversible metalloenzyme catalysis pathway.
- This contrasts with irreversible conditions typically required for chemical Birch reductions.
- The findings highlight efficient biological catalysts for redox transformations.
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