Table 1 Steady-state kinetic parameters of ancient GalDHsa,c and GULOsb,c

From: Structure, mechanism, and evolution of the last step in vitamin C biosynthesis

 

Substrate

KM (mM)

kcat (s−1)

kcat/KM (M−1 s−1)

vGalDHa

L-galactono-1,4-lactone

0.0166 ± 0.0026

18.6 ± 0.7

1.1 × 106

L-gulono-1,4-lactone

2.1 ± 0.3

8.3 ± 0.5

3.9 × 103

D-arabino-1,4-lactone

1.1 ± 0.1

16.9 ± 0.8

1.5 × 104

vGalDH A113G(oxidase)b

L-galactono-1,4-lactone

0.040 ± 0.0030

9.8 ± 0.7

2.5 × 105

L-gulono-1,4-lactone

10.4 ± 0.3

6.2 ± 0.7

6.0 × 102

D-arabino-1,4-lactone

0.13 ± 0.002

3.3 ± 0.2

2.5 × 104

vGalDH A113G(dehydrogenase)a

L-galactono-1,4-lactone

0.053 ± 0.012

17.1 ± 1.5

3.2 × 105

L-gulono−1,4-lactone

4.2 ± 0.6

7.2 ± 0.4

1.7 × 103

D-arabino−1,4-lactone

1.3 ± 0.2

10.5 ± 0.7

8 × 103

vGalDH G413Na

L-galactono-1,4-lactone

0.015 ± 0.002

7.0 ± 0.2

4.6 × 105

L-gulono-1,4-lactone

0.284 ± 0.034

2.1 ± 0.1

7.4 × 103

D-arabino-1,4-lactone

6.3 ± 0.9

5.7 ± 0.3

9 × 102

cGULOb

L-galactono-1,4-lactone

11.8 ± 1.2

3.5 ± 0.3

3.0 × 102

L-gulono-1,4-lactone

6.1 ± 0.7

3.2 ± 0.1

5.2 × 102

D-arabino-1,4-lactone

48.6 ± 24

0.6 ± 0.1

1.23 × 101

mGULOb

L-galactono-1,4-lactone

1.9 ± 0.2

4.2 ± 0.1

2.2 × 103

L-gulono−1,4-lactone

0.8 ± 0.1

6.1 ± 0.1

7.6 × 103

D-arabino-1,4-lactone

3.3 ± 0.4

0.5 ± 0.1

1.5 × 102

  1. aMeasured at 25 °C in 50 mM potassium phosphate buffer pH 8 with 50 μM cyt c. Activities below 0.2 s−1 were measured when oxygen was used in place of cytochrome c. Data for sGalDH are listed in Supplementary Table 2.
  2. bMeasured at 25 °C in 50 mM potassium phosphate buffer pH 8 by monitoring oxygen consumption. Data for jGULO and tGULO are listed in Supplementary Table 2.
  3. cSupplementary Figs. 6–17 and Source Data show the kinetic data.
Back to article page