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Table 1 Kinetic constants of St AckA catalyzed reaction

From: Structural and mechanistic investigations on Salmonella typhimurium acetate kinase (AckA): identification of a putative ligand binding pocket at the dimeric interface

Ligand

K m (mM)

V max (μmol min-1 mg-1)

k cat (s-1)

kca t/K m (s-1 mM-1)

  

Formate

13.5 ± 0.3

1180 ± 20

880 ± 105

68 ± 15

  

ATP (forrmate)a

0.085 ± 0.010

1160 ± 10

870 ± 120

10240 ± 80

  

Acetate

1.2 ± 0.1

1560 ± 18

1180 ± 75

985 ± 62

  

ATP(acetate)a

0.070 ± 0.005

1550 ± 10

1170 ± 85

16860 ± 50

  

Propionate

11.2 ± 0.1

1250 ± 12

940 ± 85

85 ± 10

  

ATP(propionate)a

0.075 ± 0.004

1230 ± 40

900 ± 135

11350 ± 50

  

Acetyl-phosphate

0.28 ± 0.04

2350 ± 30

1764 ± 25

6300 ± 45

  

ADP

0.100 ± 0.003

2340 ± 20

1750 ± 65

17645 ± 10

  

Nucleotide b

ATP

GTP

UTP

CTP

  

K m (mM)

0.070 ± 0.005

0.078 ± 0.027

0.0960 ± 0.058

0.088 ± 0.042

  

V max (μmol min-1 mg-1)

1560 ± 18

1475 ± 25

1185 ± 22

950 ± 30

  

Metal c

Mg 2+

Mn 2+

Co 2+

Ni 2+

  

[M] d

1.0 ± 0.2

1.10 ± 0.6

2.30 ± 0.3

3.50 ± 1.0

  

V max (μmol min-1 mg-1)

1560 ± 18

1590 ± 30

250 ± 25

70 ± 40

  

Inhibition

Citrate

Succinate

α-KG

2,4-DAB

2-KB

Malate

[I] (mM) e

63 ± 15

75 ± 20

7 ± 1.8

5 ± 2.2

3 ± 1.3

1 ± 0.5

V app (μmol min-1 mg-1) f

1400 ± 80

1415 ± 65

900 ± 70

650 ± 85

340 ± 50

175 ± 95

  1. Values reported are mean ± standard deviation from three independent experiments.
  2. a Formate, acetate and propionate are shown in parenthesis to indicate that the kinetic constants for ATP were determined in their presence.
  3. b Assays were performed with acetate and Mg2+.
  4. c Assays were performed with acetate and ATP.
  5. d Value of [M] represents ratio of the metal ion w.r.t. ATP, required for the maximum activity.
  6. e Value of the [I] represents concentration of the inhibitor required to reduce the catalytic activity of St AckA by 50% at the saturating concentration of cognate ligand.
  7. fV app was measured at equimolar concentrations of the substrate and inhibitor.