Abstract.
The reduction potentials of the metalloproteins pyruvate ferredoxin oxidoreductase (POR), ferredoxin, and hydrogenase isolated from hyperthermophilic Thermococcus celer (T opt=88 °C) were determined as a function of temperature from 10 to 85 °C. Square-wave voltammetry experiments were carried out on 15 µL samples directly at an unmodified "edge-polished" pyrolytic graphite electrode using MgCl2 as an electrode promoter. POR exhibited two voltammetric waves with peaks at –280 and –403 mV at room temperature, indicating multiple redox centers, and a single wave at –420 mV at 85 °C. These waves displayed different temperature-dependent peak positions and peak heights, indicating that these redox centers have different thermodynamic and kinetic properties. Ferredoxin displayed a single linear temperature-dependent voltammetric wave at –280 mV at room temperature and –327 mV at 85 °C. Hydrogenase displayed a single biphasic temperature-dependent voltammetric wave at –197 mV at room temperature and –211 mV at 85 °C. Thermodynamic parameters associated with electron transfer, namely standard enthalpies and entropies for the redox centers in the various proteins, are reported.
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Smith, E., Odom, L., Awramko, J. et al. Direct electrochemical characterization of hyperthermophilic Thermococcus celer metalloenzymes involved in hydrogen production from pyruvate. J. Biol. Inorg. Chem. 6, 227–231 (2001). https://doi.org/10.1007/s007750000179
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DOI: https://doi.org/10.1007/s007750000179