. Author manuscript; available in PMC: 2009 Apr 15.

Published in final edited form as: Arch Biochem Biophys. 2008 Feb 14;472(2):100–104. doi: 10.1016/j.abb.2008.02.012

Table 1.

Steady-state kinetic parameters for human IMPDH1 isoforms. Experiments on the retinal specific forms were conducted at 25 °C in 50 mM Tris-Cl buffered solution (pH 8.0) containing 100 mM KCl, 1 mM DTT and 3 mM EDTA. The conditions are described in Materials and Methods. N.A.: not applicable.

Enzyme	k_cat (s⁻¹)	K_m (IMP) (μM)	K_m (NAD⁺) (μM)	K_ii (NAD⁺) (mM)
IMPDH1(546)	0.22 ± 0.03	15 ± 4	22 ± 3	N.A.
IMPDH1(546)-D226N	0.24 ± 0.03	11 ± 1	24 ± 3	6 ± 4
IMPDH1(595)	0.18 ± 0.03	11 ± 1	26 ± 4	N.A.
IMPDH1(595)-D226N	0.22 ± 0.03	10 ± 1	16 ± 2	N.A.
IMPDH1(514)	0.31 ± 0.03	4 ± 1	14 ± 2	0.51 ± 0.07
IMPDH1(514)^*	1.2 ± 0.4	17 ± 2	70 ± 10	2.0 ± 0.6
IMPDH1(514)-D226N^*	0.7 ± 0.2	12 ± 2	50 ± 10	4 ± 2

Data from Ref. [12], measured at 37°C.