Table 2 Kinetic parameters of the α2βγ, αβ and αγ enzymes in the absence of any regulators.

From: The β and γ subunits play distinct functional roles in the α2βγ heterotetramer of human NAD-dependent isocitrate dehydrogenase

Enzyme

V max,ICT

S 0.5,ICT

Hill coefficient for ICT

S 0.5,Mn

S 0.5,NAD

k cat a

k cat /S 0.5,ICT

μmol/mg/min

mM

μM

μM

s −1

s −1 mM −1

α2βγ

20.0 ± 0.1

2.35 ± 0.05

2.0 ± 0.1

60.2 ± 6.0

143 ± 5

26.7 ± 0.1

11.36 ± 0.04

αβ

10.9 ± 0.3

13.4 ± 0.1

1.1 ± 0.0

5305 ± 314

326 ± 15

14.6 ± 0.4

1.08 ± 0.03

αγ

7.29 ± 0.11

4.49 ± 0.15

2.0 ± 0.1

95.1 ± 3.2

238 ± 18

9.72 ± 0.15

2.16 ± 0.03

  1. The Vmax and S0.5 of the α2βγ and αγ enzymes were determined at the standard conditions with varied concentrations of ICT, or MnCl2, or NAD. The Vmax and S0.5 of the αβ enzyme were determined at the same conditions but with higher concentration of MnCl2 (50 mM).
  2. aA molecular mass of 80 kDa was used to calculate the mole of enzyme in heterodimeric form per mg of protein (1.25 × 10−8 mol of dimeric enzyme/mg of protein).
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