23.07.09 Prof. Matthias Boll, Leipzig
Dearomatizing benzoyl-coenzyme A reductases in anaerobes: catalysts of a biological Birch-reduction
| What |
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| When |
23.07.2009 from 05:15 to 06:00 |
| Where | SR 1007, Albertstr. 21, 10. OG |
| Contact Name | Angelika Massler |
| Contact Phone | 203 6090 |
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The Birch reduction is a widely used synthetic tool to achieve dihydro additions to aromatic compounds and proceeds in single electron transfer/protonation steps. It requires solvated electrons as donors, the most potent reductants known in organic chemistry. An analogous reaction is catalyzed by benzoyl-CoA reductases (BCR), which stereospecifically dearomatize the CoA ester substrate to a cyclic trans dihydro product. BCR are key enzymes in the degradation of aromatic compounds in anaerobic bacteria. There are two completely different classes of BCR: (i) soluble BCRs from facultative anaerobes couple electron transfer from reduced ferredoxin to the aromatic ring to a stoichiometric ATP hydrolysis; they contain three [4Fe‑4S] clusters. (ii) BCRs from obligate anaerobes have only very recently been discovered and have a completely different composition. The active site subunits contain a W-pterin cofactor and four [4Fe-4S] clusters. An association with additional modules with similarities to heterodisulfide reductases/NADH:quinone oxidoreductases is expected. Most importantly, the reaction of BCRs from obligate anaerobes is independent of ATP hydrolysis and reversible. In spite of their different compositions both BCR classes yield the same dienoyl-CoA product.