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Table 1 Kinetic parameters, Vmax and Km, of α-IPMS reacting to α-ketoisovaleric acid and acetyl CoAa

From: Characterization of α-isopropylmalate synthases containing different copy numbers of tandem repeats in Mycobacterium tuberculosis

α-IPMS α-Ketoisovaleric acid Acetyl CoA
  Km
(μM)
Vmax
(U/mg protein)
R2 k cat b
(s-1)
k cat /Km
(s-1 M-1)
Km
(μM)
Vmax
(U/mg protein)
R2 k cat b
(s-1)
k cat /Km
(s-1 M-1)
α-IPMS-2CR 261
(S.E. = 14.7)
0.49
(S.E. = 0.01)
0.99 1.17 4480 568
(S.E. = 94.5)
0.93
(S.E. = 0.06)
0.99 2.22 3,900
α-IPMS-14CR 35
(S.E. = 5.4)
0.16
(S.E. = 0.01)
0.96 0.52 14,800 27
(S.E. = 6.9)
0.19
(S.E. = 0.01)
0.93 0.61 22,590
  1. a At pH 8.5 and 37°C. The apparent Km and Vmax values were determined by varying the concentrations of one substrate at a fixed saturating concentration of the other substrate. α-ketoisovaleric acid and acetyl CoA was fixed at 2 mM and 0.8 mM, respectively. Data are the average of two assays. Prism software (version 3.08) was used for nonlinear regression, curve fit analysis to calculate Km and Vmax.
  2. bk cat = Vmax/[E] (μmol s-1mg-1)/(mol mg-1)