TABLE 2

Thermodynamics of biochemical reactions involved in conversion of lactate to butyrate, hexanoate, and octanoatea

Equation no.EquationAssociated
MAG(s)
ΔG per mol substrateb (kJ mol−1)YATP (mol ATP mol−1
substrate)b,c
ΔG0' available
per ATP
producedd
(kJ mol−1 ATP)
Terminal
enzyme
PH2 = 10−6
atm
PH2 = 1 atmPH2 = 6.8 atm
Lactate elongation
    192 C3H5O3- + 1 H+ → 1 C4H7O2-
+ 2 CO2 + 2 H2
EUB1−62−26−210.75−29 to −82CoAT
    203 C3H5O3- + 2 H+ → 1 C6H11O2-
+ 3 CO2 + 2 H2 + 1 H2O
EUB1−58−34−310.83−37 to −70CoAT
    214 C3H5O3- + 3 H+ → 1 C8H15O2-
+ 4 CO2 + 2 H2 + 2 H2O
EUB1−57−39−360.88−41 to −64CoAT
    222 C3H5O3- + 1 H+ → 1 C4H7O2-
+ 2 CO2 + 2 H2
EUB1−62−26−210.25−86 to −247TE
    233 C3H5O3- + 2 H+ → 1 C6H11O2-
+ 3 CO2 + 2 H2 + 1 H2O
EUB1−58−34−310.50−62 to −116TE
    244 C3H5O3- + 3 H+ → 1 C8H15O2-
+ 4 CO2 + 2 H2 + 2 H2O
EUB1−57−39−360.63−58 to −90TE
Lactate and
C2/C4/C6g
elongation
    251 C3H5O3- + 1 C2H3O2- + 1 H+
1 C4H7O2- + 1 CO2 + 1 H2O
EUB1−50−50−501.00−50 to −50CoAT
    262 C3H5O3- + 1 C2H3O2- + 2 H+
1 C6H11O2- + 2 CO2 + 2 H2O
EUB1−50−50−501.00−50 to −50CoAT
    273 C3H5O3- + 1 C2H3O2- + 3 H+
1 C8H15O2- + 3 CO2 + 3 H2O
EUB1−51−51−511.00−51 to −51CoAT
    281 C3H5O3- + 1 C4H7O2- + 1 H+
1 C6H11O2- + 1 CO2 + 1 H2O
EUB1−50−50−501.00−50 to −50CoAT
    292 C3H5O3- + 1 C4H7O2- + 2 H+
1 C8H15O2- + 2 CO2 + 2 H2O
EUB1−51−51−511.00−51 to −51CoAT
    301 C3H5O3- + 1 C6H11O2- + 1 H+
1 C8H15O2- + 1 CO2 + 1 H2O
EUB1−53−53−531.00−53 to −53CoAT
    311 C3H5O3- + 1 C2H3O2- + 1 H+
1 C4H7O2- + 1 CO2 + 1 H2O
Nonef−50−50−500.00NAfTE
    322 C3H5O3- + 1 C2H3O2- + 2 H+
1 C6H11O2- + 2 CO2 + 2 H2O
Nonee−50−50−500.50−100 to −100TE
    333 C3H5O3- + 1 C2H3O2- + 3 H+
1 C8H15O2- + 3 CO2 + 3 H2O
Nonee−51−51−510.67−76 to −76TE
    341 C3H5O3- + 1 C4H7O2- + 1 H+
1 C6H11O2- + 1 CO2 + 1 H2O
Nonee−50−50−500.00NAfTE
    352 C3H5O3- + 1 C4H7O2- + 2 H+
1 C8H15O2- + 2 CO2 + 2 H2O
Nonee−51−51−510.50−103 to −103TE
    361 C3H5O3- + 1 C6H11O2- + 1 H+
1 C8H15O2- + 1 CO2 + 1 H2O
Nonef−53−53−530.00NAfTE
  • a Free energies of formation for all chemical compounds were obtained from Kbase (www.kbase.us). The ATP yield was determined on the basis of biochemical models presented in Data Set S7 and is indicated as moles of ATP produced per mole of lactate consumed. The terminal enzyme of reverse β-oxidation, i.e., either a CoA transferase (CoAT) or thioesterase (TE), is also indicated.

  • b ΔG values and expected ATP yields are normalized to moles of xylose, moles of lactate, or moles of glycerol.

  • c Pathway reconstructions shown in Data Set S7 were used to determine the expected ATP yields.

  • d The minimum expected level of ΔG0' per mole of ATP produced is −60 kJ. Values below this are indicated by bold text and indicate that the predicted ATP yield exceeds what is physiologically feasible.

  • e The proposed model requires acetate kinase either for incorporation of a carboxylate or for ATP generation from acetyl-CoA. EUB1 is not predicted to produce this enzyme.

  • f NA, no net ATP production is predicted for this model.

  • g These scenarios considered coutilization of lactate and acetate (C2), butyrate (C4), or hexanoate (C6).