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Table 1 Kinetic parameters of maize HXKs

From: Biochemical properties and subcellular localization of six members of the HXK family in maize and its metabolic contribution to embryo germination

Protein

Parametera

Substrate

Glucose

Fructose

Mannose

ATP

ZmHXK4Δ30

V max

5.65 ± 0.12

3.05 ± 0.46

3.23 ± 0.22

1.83 ± 0.35

K m

195.70 ± 31.96

19,324.15 ± 3914.89

138.85 ± 22.42

134.90 ± 25.74

k cat /K m

2.85 × 104

1.55 × 102

2.29 × 104

1.34 × 104

ZmHXK5Δ30

V max

4.55 ± 0.34

2.49 ± 0.29

2.77 ± 0.19

1.54 ± 0.56

K m

136.65 ± 20.01

30,216.8. ± 5708.76

119.55 ± 33.30

135.60 ± 11.46

kcat/Km

3.27 × 104

81.00

2.28 × 104

1.12 × 104

ZmHXK6Δ30

V max

3.60 ± 0.14

2.61 ± 0.47

3.08 ± 0.33

1.08 ± 0.32

K m

65.86 ± 15.19

4291.84 ± 1410.04

48.85 ± 1.06

198.85 ± 12.80

k cat /K m

5.40 × 104

6.01 × 102

6.23 × 104

5.36 × 103

ZmHXK7

V max

27.19 ± 0.77

23.44 ± 0.30

21.33 ± 0.54

13.21 ± 0.48

K m

108.10 ± 17.96

2701.85 ± 590.93

123.79 ± 11.61

28.74 ± 0.30

k cat /K m

2.46 × 105

8.48 × 103

1.68 × 105

4.49 × 105

ZmHXK8

V max

17.38 ± 0.24

NC

14.79 ± 0.99

10.91 ± 0.34

K m

4687 ± 299.53

NC

10,396.50 ± 54.31

147.20 ± 62.08

k cat /K m

3.66 × 103

NC

1.40 × 103

7.32 × 104

  1. aVmax is expressed in μmol hexose-6-P min− 1 mg− 1; Km is expressed in μM and kcat/Km in M− 1 s− 1; NC: Non-calculated since the enzyme does not reach the saturation
  2. To obtain the Km for hexoses the ATP concentration was fixed at 2 mM. To obtain the Km for ATP, Glc was used at a fixed concentration of 5 mM except for ZmHXK8 that was fixed at 50 mM Glc. The kinetic parameters were obtained with Origin 8.0 software and the values represent the average ± standard deviation of two technical repeats from three independent replicates