Archives of Microbiology

, Volume 155, Issue 4, pp 378–381

Thermodynamics of methylenetetrahydrofolate reduction to methyltetrahydrofolate and its implications for the energy metabolism of homoacetogenic bacteria

  • Gert Wohlfarth
  • Gabriele Diekert
Original Papers

Abstract

The thermodynamics of the methylenetetrahydrofolate reduction to 5-methyltetrahydrofolate was studied with the methylenetetrahydrofolate reductase purified from the homoacetogenic bacterium Peptostreptococcus productus. The equilibrium constants were determined for the forward and backward reactions of methylenetetrahydrofolate reduction with NADH or acetylpyridine adenine dinucleotide (APADH), respectively, as the electron donors. From the equilibrium constants and the known standard redox potentials at pH 7 (Eo′) of the couples NAD+/NADH or APAD+/APADH the Eo′ of the couple methylene-/methyltetrahydrofolate was determined to be about-200mV. This value is different from values reported before for this couple. The implications for the mechanism of energy conservation of homoacetogens is discussed.

Key words

Methylenetetrahydrofolate Methyltetrahydrofolate Methylenetetrahydrofolate reductase Homoacetogenic bacteria Energy conservation of homoacetogens 

Abbreviations

FH4

tetrahydrofolate

CH2=FH4

5,10-methylenetrahydrofolate

CH3-FH4

5-methyltetrahydrofolate

Keq

equilibrium constant

ΔGo

Gibb's free energy change under standard conditions (all concentrations of reactants = 1 M)

ΔGo′

ΔGo at pH 7 ([H+]=10-7 M)

Eo

standard redox potential

ΔGo

standard redox potential difference of two reactants

ΔEo′

ΔEo at pH 7

R

gas constant

F

Faraday constant

APAD

acetylpyridine adenine dinucleotide (NAD+-analogue)

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Gert Wohlfarth
    • 1
  • Gabriele Diekert
    • 1
  1. 1.Institut für MikrobiologieUniversität StuttgartStuttgart 1Federal Republic of Germany

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