Table 1.

Values of k_cat for EcGMPR reactions.

Parameter	kcat (s−1)
	wild-type	C186A	T188A	E289Q
GMP + NADPH	0.35 ± 0.01	≤ 0.0001 b	(8.8 ± 0.6)×10−4 b	(3.8 ± 0.3)×10−4 b,c
2-Cl-IMP + NADPH	0.40 ± 0.01	≤ 0.0001 d	0.021 ± 0.001 d	0.027 ± 0.001 d
GMP + APADPH	< 0.0008	n.d.	n.d.	n.d.
2-Cl-IMP + APADPH	0.08 ± 0.01	n.d.	n.d.	n.d.

^aReactions were performed in 75 mM Tris, pH 7.8, 100 mM KCl, 1 mM DTT, and 1 mM EDTA at 25°C. NADPH consumption was monitored as described in Methods. Values are the average and standard error of at least two independent experiments. n.d., no data.

^bThese reactions were performed at saturating concentrations of GMP (1 mM) and NADPH (1 mM).

^cA complete turnover was not observed.

^dThese assays were conducted at saturating concentrations of 2-Cl-IMP (0.8 mM) and NADPH (1 mM).