Reversible Biological Birch Reduction at an Extremely Low Redox Potential
详细信息 查看全文
- 作者：Johannes W. Kung ; Sven Baumann ; Martin von Bergen ; Michael Mller ; Peter-Leon Hagedoorn ; Wilfred R. Hagen ; Matthias Boll
- 刊名：Journal of the American Chemical Society
- 出版年：2010
- 出版时间：July 21, 2010
- 年：2010
- 卷：132
- 期：28
- 页码：9850-9856
- 全文大小：282K
- 年卷期：v.132,no.28(July 21, 2010)
- ISSN：1520-5126
文摘
The Birch reduction of aromatic rings to cyclohexadiene compounds is widely used in chemical synthesis and requires solvated electrons, the most potent reductants known in organic chemistry. Benzoyl-coenzyme A (CoA) reductases (BCR) are key enzymes in the anaerobic bacterial degradation of aromatic compounds and catalyze an analogous reaction under physiological conditions. Class I BCRs are FeS enzymes and couple the reductive dearomatization of benzoyl-CoA to cyclohexa-1,5-diene-1-carboxyl-CoA (dienoyl-CoA) to a stoichiometric ATP hydrolysis. Here, we report on a tungsten-containing class II BCR from Geobacter metallireducens that catalyzed the fully reversible, ATP-independent dearomatization of benzoyl-CoA to dienoyl-CoA. BCR additionally catalyzed the disproportionation of dienoyl-CoA to benzoyl-CoA/monoenoyl-CoA and the four- and six-electron reduction of benzoyl-CoA in the presence of a reduced low-potential bridged 2,2′-bipyridyl redox dye. Reversible redox titration experiments in the presence of this redox dye revealed a midpoint potential of E0′= −622 mV for the benzoyl-CoA/dienoyl-CoA couple, which is far below the values of other known reversible substrate/product redox couples in enzymology. This work demonstrates the efficiency of reversible metalloenzyme catalysis, which in chemical synthesis can only be achieved under essentially irreversible conditions.