title: Direct electrochemical characterization of hyperthermophilic Thermococcus celer metalloenzymes involved in hydrogen production from pyruvate.
abstract: The reduction potentials of the metalloproteins pyruvate ferredoxin oxidoreductase (POR), ferredoxin, and hydrogenase isolated from hyperthermophilic Thermococcus celer (Topt = 88 degrees C) were determined as a function of temperature from 10 to 85 degrees C. Square-wave voltammetry experiments were carried out on 15 microL 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 degrees 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 degrees C. Hydrogenase displayed a single biphasic temperature-dependent voltammetric wave at -197 mV at room temperature and -211 mV at 85 degrees C. Thermodynamic parameters associated with electron transfer, namely standard enthalpies and entropies for the redox centers in the various proteins, are reported.
authors: Department of Chemistry, Hamline University, St. Paul, MN 55104-1284, USA. gsmith@gw.hamline.edu
authors: E T
authors: ET
authors: Smith
authors: L D
authors: LD
authors: Odom
authors: J A
authors: JA
authors: Awramko
authors: M
authors: M
authors: Chiong
authors: J
authors: J
authors: Blamey
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D008667:Metalloproteins / Q000737:chemistry / Q000378:metabolism*; D050743:Pyruvate Synthase; D019289:Pyruvic Acid / Q000378:metabolism*; D019712:Thermococcus / Q000378:metabolism*
chemical_list: D005288:Ferredoxins; D008667:Metalloproteins; D006859:Hydrogen; D019289:Pyruvic Acid; D006864:Hydrogenase; D007658:Ketone Oxidoreductases; D050743:Pyruvate Synthase