Table 1. Steady-state kinetic parameters for the normal reaction catalyzed by IDH1, conversion of ICT to αKG, and for the neomorphic reaction catalyzed by IDH1, conversion of αKG to D2HG.

At least two enzyme preparations were used to obtain k_obs rates (at 37°C), which were plotted against substrate concentration and fit to a hyperbolic function. The SE shown is determined from the deviation resulting from hyperbolic fits of plots of k_obs versus substrate concentration in order to calculate catalytic efficiency (k_cat/K_M, mM⁻¹ s⁻¹). In some cases, maximal rates were still achieved at concentrations of NADPH that approached the limit of detection, and thus, K_M values are listed as ≤ or < than the lowest concentration tested.

IDH1	kcat (s−1), ICT → αKG	KM, ICT (mM) ICT → αKG	KM, NADP+ (mM) ICT → αKG	kcat/KM (mM−1 s−1) ICT → αKG	kcat (s−1) αKG → D2HG	KM, αKG (mM) αKG → D2HG	KM, NADPH (mM) αKG → D2HG	kcat/KM (mM−1 s−1) αKG → D2HG
WT [17]	85 ± 4	0.22 ± 0.02	0.08 ± 0.03	3.9 × 102 ± 0.4 × 102	0.019 ± 0.001	0.5 ± 0.3	<0.010	0.04 ± 0.02
R132H [17]	2.4 ± 0.1	4.2 ± 0.6	1.6 ± 0.5	0.57 ± 0.08	1.44 ± 0.051	1.5 ± 0.21	<0.025	1.0 ± 0.11
R132C [17]	4.4 ± 0.1	8.2 ± 0.8	0.75 ± 0.07	0.54 ± 0.05	1.60 ± 0.07	0.36 ± 0.05	0.010 ± 0.009	4.4 ± 0.6
R132G [17]	9.3 ±0.6	7 ± 1	0.067 ± 0.007	1.3 ± 0.2	1.59 ± 0.09	0.34 ± 0.08	<0.025	5 ± 1
R132Q [17]	9.2 ±0.3	0.8 ± 0.2	0.22 ± 0.052	12 ± 3	4.7 ± 0.2	0.26 ± 0.04	<0.0052	18 ± 3
R132L	4.0 ± 0.1	2.2 ± 0.2	0.055 ± 0.009	1.8 ± 0.2	0.79 ± 0.05	0.05 ± 0.01	<0.005	16 ± 3
R132S	5.6 ± 0.2	3.9 ± 0.7	0.059 ± 0.009	1.4 ± 0.3	1.32 ± 0.07	0.20 ± 0.04	<0.005	7 ± 1
R132V	1.38 ± 0.09	1.6 ± 0.4	0.073 ± 0.008	0.9 ± 0.2	1.10 ± 0.01	0.134 ± 0.006	<0.005	8.2 ± 0.4

¹Additional measurements have led to slight adjustment in previously reported values.

²Not reported previously.