Radicals in anaerobic aromatic metabolism

• Applicant: Professor Dr. Matthias Boll
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 1999 to 2007
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5177562

The role of radicals in enzyme catalysis will be studied with two enzymes of anaerobic aromatic metabolism in the bacterium Thauera aromatica. (1) Benzoyl-CoA reductase reduces the aromatic ring by coupling electron transfer to ATP-hydrolysis. This reaction is thought to be similar to a Birch reduction. This model implies alternate one-electron transfer and protonation steps, with E'o of the first electron transfer of -1.9 V. The 'Birch' hypothesis will be probed by altering the electronic characteristics of the substrate, by the use of of inhibitors and isotopes and by the detection of kinetic isotope effects. Intermediate substrates and/or enzyme radicals will be detected by EPF-, ENDOR- and FT-IR spectroscopic techniques. For comparison, ring reducing enzymes will be studied from anaerobic bacteria which are thought to transfer electrons without coupling to ATP hydrolysis. (2) Phenylphosphate carboxylase catalyzes phenylphosphate para-carboxylation to 4-hydroxybenzoate and 14CO2/carboxylate isotope exchange. The enzyme which is sensitive towards oxygen and radical trapping agents will be purified and the potential radical reaction mechanism will be investigated by similar methods as described for benzoyl-CoA reductase.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1071: Radikale in der enzymatischen Katalyse