TABLE 1

List of standard redox potentials for key F420-linked redox reactionsa

SubstratebReactionE0′ (mV)Reference
FerredoxinFd + 2 e → Fd2−−500 to −400487
CO2/formateCO2 + 2 e + H+ → HCO2−420487
H+/H22 H+ + 2 e → H2−410487
Methenyl/methylene H4MPTCHEmbedded ImageH4MPT + 2 e + H+ → CH2=H4MPT−390301
F420F420 + 2 e + 2 H+ → F420H2−3408
6PGL/G6P6-Phosphogluconolactone + 2 e + 2 H+ → Glucose-6-phosphate−330488
Methylene/methyl H4MPTCH2=H4MPT + 2 e + H+ → CH3-H4MPT−320301
NAD(P)+NAD(P)+ + 2 e + H+ → F420H2−320487
Acetone/propan-2-olAcetone + 2 e + 2 H+ → Propan-2-ol−29053
FADFAD + 2 e + 2 H+ → FADH2−22053
RiboflavinRiboflavinox + 2 e + 2 H+ → Riboflavinred−21053
FMNFMN + 2 e + 2 H+ → FMNH2−19053
MethanophenazineMphenox + 2 e + 2 H+ → Mphenred−170489
HeterodisulfideCoM-S-S-CoB + 2 e + 2 H+ → CoM-SH + CoB-SH−140487
Sulfite/sulfideSO3 + 6 H+ + 6 e → S + 3 H2O−120490
MenaquinoneMenaquinone + 2 e + 2 H+ → Menaquinol−7053
O2/H2OO2 + 4 H+ + 4 e → 2 H2O+82053
  • a This list of standard redox potentials (E0′) demonstrates that the electrochemical properties of F420 enable the cofactor to mediate a wide range of oxidation and reduction reactions in biological systems, especially methanogenic archaea. In whole cells, physiological redox potentials can differ considerably due to the mass action ratios of substrates/products and differences in physical conditions (487). Potentials were determined under standard conditions (25°C, 1 atm, pH 7.0) against the standard hydrogen electrode.

  • b 6PGL, 6-phosphogluconolactone; Mphenox and Mphenred, oxidized and reduced methanophenazine, respectively.