TABLE 1

Thermodynamics of biochemical reactions involved in conversion of xylose 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
produced
(kJ mol−1 ATP)
Terminal
enzyme
PH2 = 10–6 atmPH2 = 1 atmPH2 = 6.8 atm
Xylose simple
fermentation
    13 C5H10O5 → 5 C3H5O3- + 5 H+LAC1, LAC2,
LAC4, LAC5
−174−174−1741.67−104 to −104
    23 C5H10O5 → 3 C3H5O3- + 3 C2H3O2-
+ 6 H+
LAC1, LAC2,
LAC4, LAC5
−214−214−2142.00−107 to −107
Xylose elongation
    33 C5H10O5 → 3 C4H7O2- + 3 CO2
+ 3 H2O + 3 H+
LCO1−264−264−2643.00−88 to −88CoAT
    43 C5H10O5 → 1 C6H11O2- +3 C2H3O2-
+ 3 CO2 + 4 H+ + 2 H2
LCO1−272−248−2452.83−87 to −96CoAT
    53 C5H10O5 → 1 C8H15O2- + 2 C2H3O2-
+ 3 CO2 + 3 H2O + 3 H+
LCO1−265−265−2653.00−88 to −88CoAT
    62 C5H10O5 → 1 C4H7O2- + 2 C2H3O2-
+ 2 CO2 + 3 H++ 2 H2
LCO1−276−240−2352.25−105 to −123TE
    73 C5H10O5 → 1 C6H11O2- + 3 C2H3O2-
+ 3 CO2 + 1 H2O + 4 H+ + 2 H2
LCO1−272−248−2452.50−98 to −109TE
    84 C5H10O5 → 1 C8H15O2- + 4 C2H3O2-
+ 4 CO2 + 2 H2O + 5 H++ 2 H2
LCO1−270−253−2502.63−95 to −103TE
Xylose and
C2/C4/C6d
elongation
    91 C5H10O5 + 2 C2H3O2- + 2 H2
2 C4H5O2- + 1 CO2 + 3 H2O
LCO1−240−311−3203.50−69 to −92CoAT
    101 C5H10O5 + 1 C2H3O2- + 2 H2
1 C6H11O2- + 1 CO2 + 3 H2O
LCO1−240−311−3203.50−69 to −92CoAT
    111 C5H10O5 + 1 C4H7O2- + 2 H2
1 C8H15O2- + 1 CO2 + 3 H2O
LCO1−264−264−2643.50−75 to −75CoAT
    121 C5H10O5 + 1 C4H7O2- → 1 C6H11O2-
+ 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+
LCO1−243−314−3243.00−81 to −108CoAT
    131 C5H10O5 + 1 C6H11O2- → 1 C8H15O2-
+ 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+
LCO1−267−267−2673.00−89 to −89CoAT
    141 C5H10O5 + 2 C2H3O2- + 2 H2
2 C4H5O2- + 1 CO2 + 3 H2O
LCO1−240−311−3201.50−160 to −214TE
    151 C5H10O5 + 1 C2H3O2- + 2 H2
1 C6H11O2- + 1 CO2 + 3 H2O
LCO1−240−311−3202.50−96 to −128TE
    161 C5H10O5 + 1 C4H7O2- + 2 H2
1 C8H15O2- + 1 CO2 + 3 H2O
LCO1−264−264−2642.50−105 to −105TE
    171 C5H10O5 + 1 C4H7O2- → 1 C6H11O2-
+ 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+
LCO1−243−314−3242.00−122 to −162TE
    181 C5H10O5 + 1 C6H11O2- → 1 C8H15O2-
+ 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+
LCO1−267−267−2672.00−133 to −133TE
  • a Free energies of formation for all chemical compounds were obtained from Kbase (www.kbase.us). The ATP yield (YATP) was determined on the basis of biochemical models presented in Data Set S7 and is indicated as moles of ATP produced per mole of xylose 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 The pathway reconstructions shown in Data Set S7 were used to determine the expected ATP yields.

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