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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