Table 1

Kinetic constants of StAckA catalyzed reaction
Ligand Km(mM) Vmax(μmol min-1mg-1) kcat(s-1) kcat/Km(s-1mM-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
Nucleotideb ATP GTP UTP CTP
Km (mM) 0.070 ± 0.005 0.078 ± 0.027 0.0960 ± 0.058 0.088 ± 0.042
Vmax (μmol min-1 mg-1) 1560 ± 18 1475 ± 25 1185 ± 22 950 ± 30
Metalc Mg2+ Mn2+ Co2+ Ni2+
[M] d 1.0 ± 0.2 1.10 ± 0.6 2.30 ± 0.3 3.50 ± 1.0
Vmax (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
Vapp (μmol min-1 mg-1) f 1400 ± 80 1415 ± 65 900 ± 70 650 ± 85 340 ± 50 175 ± 95

Values reported are mean ± standard deviation from three independent experiments.

a Formate, acetate and propionate are shown in parenthesis to indicate that the kinetic constants for ATP were determined in their presence.

b Assays were performed with acetate and Mg2+.

c Assays were performed with acetate and ATP.

d Value of [M] represents ratio of the metal ion w.r.t. ATP, required for the maximum activity.

e Value of the [I] represents concentration of the inhibitor required to reduce the catalytic activity of StAckA by 50% at the saturating concentration of cognate ligand.

fVapp was measured at equimolar concentrations of the substrate and inhibitor.

Chittori et al.

Chittori et al. BMC Structural Biology 2012 12:24   doi:10.1186/1472-6807-12-24

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