Table 3.

Kinetic and Thermodynamic Parameters

		steady state parametersa				equilibrium bindingb
enzyme	ligand	Km (μM)	Hill coefficient (h)	kcat (s–1)	Ki (μM)	Hill coefficient (h)	Kd (nM)
KPR	KP	9.6 ± 0.7	1.0	16.6 ± 0.6	270 ± 40	–	–
	NADPH	7.2 ± 0.2	2.5 ± 0.2	16.8 ± 0.3	–	1.28 ± 0.05c	58 ± 2c
						1.22 ± 0.06d	84 ± 4d
						1.27 ± 0.02e	117 ± 2e
KPRA181L	KP	8100 ± 100	0.77 ± 0.03	18.2 ± 0.8	–	–	–
	NADPH	5.7 ± 0.4	1.0	16.4 ± 0.3	–	–	–

^aFit to eq 1 or 2 in Materials and Methods.

^bNADPH binding to KPR fit to eq 6 or 11 in Materials and Methods.

^cBased on FRET analysis (see Figure 5E).

^dBased on Trp167 quenching (see Figure 5F).

^eBased on a model-independent binding isotherm (see Figure 6).