CtXR^{a}

NAD(H) (R
_{1})

NADP(H) (R
_{2})


E

PO^{b}

PO^{b}

V
_{f}

1.0

1.3

V
_{f}/V
_{r}

13

25

K
_{iA} (mM)

0.18 ± 0.04

0.0019 ± 0.0001^{c}

K
_{mA} (mM)

0.04 ± 0.01

0.005 ± 0.002

K
_{mB} (mM)

98 ± 22

108 ± 17

K
_{iB} (mM)^{d}

392

3920

K
_{iQ} (mM)

0.344 ± 0.03

0.0059 ± 0.0004^{c}

K
_{mQ} (mM)

0.019 ± 0.005

0.008 ± 0.001

K
_{mP} (mM)

529 ± 34

220 ± 18

K
_{iP} (mM)

758 ± 48

556 ± 48

K
^{Haldane, e}_{eq}

134

142

K
^{exp, e}_{eq}

142

156

GmXDH^{f}(R
_{3})
 
PP (R
_{5}), UG (R
_{9}), LG (R
_{10})
 

E

PO^{b}

V
_{f}

PO^{b}

V
_{f}

1.0

K
_{m} (mM)

0.1

V
_{r}

12.6
  
\({K_{\rm{m,NAD}^{+}}}\) (mM)

0.14

PGI^{h} (R
_{6})
 
K
_{m,xylitol} (mM)

14

V
_{f}

PO^{b}

\({K_{\rm{i,NAD}^{+}}}\) (mM)

0.78

K
_{m,F6P} (mM)

0.15

K
_{i,xylitol} (mM)^{d}

4.5

K
_{m,G6P} (mM)

0.30

K
_{i,NADH} (mM)

0.025

K
_{eq}

3.23

K
_{m,NADH} (mM)

0.073
  
K
_{m,xylulose} (mM)

4.0

G6PDH (R
_{7})
 
K
_{i,xylulose} (mM)^{g}

1.0

V
_{f}

PO^{b}

K
^{Haldane, e}_{eq}

7 × 10^{−4}

\({K_{\rm{m,NADP}^{+}}}\) (mM)

0.1

K
^{exp, e}_{eq}

(47) × 10^{−4}

K
^{h}_{m,G6P}
(mM)

0.05

 
K
_{i,NADPH} (mM)

0.20 (0.05)^{i}

XK (R
_{4})
   
V
_{f}

PO^{b}

GND (R
_{8})
 
K
_{m,xylulose} (mM)^{h}

0.31

V
_{f}

PO^{b}

 
K
^{+}_{m,NADP}
(mM)

0.02

 
K
^{h}_{m,6PG}
(mM)

0.05

 
K
_{i,NADPH} (mM)

0.02


^{a}A, B, P, Q relate to NAD(P)H, xylose, xylitol, and NAD(P)^{+}, respectively

^{b}PO, values were found within a predefined range by parameter optimization (see main text and Additional file 1: Table S3)

^{c}Values obtained from ligandbinding analysis using fluorescence spectroscopy (this study)

^{d}Values calculated from Haldane relationship K
_{eq} = V
^{2}_{f}
K
_{iP}
K
_{mQ}/(V
^{2}_{r}
K
_{iB}
K
_{mA}) [38]

^{e}Equilibrium constants were calculated in accordance with the Haldane relationship [K
^{Haldane}_{eq}
= V
_{f}
K
_{mP}
K
_{iQ}/(V
_{r}
K
_{mB}
K
_{iA})] [38]. Values can be compared to those experimentally obtained in this study (CtXR) or to reported K
^{exp}_{eq}
[39, 40]. Calculated Gibbs free energies of reaction of 6 ± 1 kJ mol^{−1} for the isomerization of xylose into xylulose [ΔG
_{r} = −RTln(K
^{Haldane}_{eqXR}
K
^{Haldane}_{eqXDH}
] or ΔG
_{r} = −RTln(K
^{exp}_{eqXR}
K
^{exp}_{eqXDH}
) are in excellence accordance with a value of 4.3 kJ mol^{−1} calculated from standard transformed Gibbs free energies of formation [41]

^{f}Reported kinetic parameters obtained from comprehensive fullkinetic study acquired at 25 °C in 50 mM potassium phosphate buffer pH 7.5 were applied [42]. A, B, P, and Q correspond to NAD^{+}, xylitol, xylulose, and NADH, respectively. Note, to fulfill thermodynamic with respect to K
^{exp}_{eq}
reported upper limits were used for V
_{r} (1800 ± 350 s^{−1}), K
_{B} (12 ± 2 mM) and lower limits for K
_{P} (8 ± 4 mM)

^{g}Value was taken from [43]

^{h}Values of kinetic parameters for XK, G6PDH, 6PGDH, and PGI were from Refs. [33, 44–46], respectively

^{i}Value referred to CBS4435 (BP000). Note based on a sensitivity analysis implemented in Copasi K
_{i} of both ScG6PDH and CtG6PDH did not significantly influence FCC and YCC