Figure 2.

Enzymes, coenzymes, and prosthetic groups involved in the energy metabolism of Methanothermobacter marburgensis and Methanothermobacter thermautotrophicus during growth on H₂ and CO₂. For the synthesis of these components, more than 200 coding sequences are required. A stoichiometry of 4 Na⁺/ATP of the A₁A₀-ATP synthase AhaA-IK was assumed to yield 0.5 ATP for every methane generated. This is also predicted from the thermodynamics at physiological H₂ concentrations. MFR, methanofuran; H₄MPT, tetrahydromethanopterin; CHO-MFR, formyl-MFR; CHO-H₄MPT, formy-H₄MPT; CH ≡ H₄MPT⁺, methenyl-H₄MPT⁺; CH₂ = H₄MPT, methylene-H₄MPT; CH₃-H₄MPT, methyl-H₄MPT; Fd, ferredoxin.