Table 2.

Equilibrium and kinetic parameters for the binding reaction of WT and R212A CYP3A4 with ritonavir and its analogs.

	DAR		DTMCR		Ritonavir
	WT	R212A	WT	R212A	WT	R212A
Ksa, μM	0.5 ± 0.1	2.2 ± 0.2	3.6 ± 0.2	6.6 ± 0.4	0.05 ± 0.01b	0.064 ± 0.008
Kdc, μM	–d	–	0.16 ± 0.04	–	–	–
kfaste, s−1	0.29 ± 0.03	0.15 ± 0.02	1.0 ± 0.1	0.70 ± 0.03	1.4 ± 0.2	1.1 ± 0.2
kslowf, s−1	0.07 ± 0.01	0.030 ± 0.002	0.13 ± 0.02	0.07 ± 0.01	0.19 ± 0.03	0.22 ± 0.02

^aSpectroscopic dissociation constant.

^bDetermined previously [7].

^cKinetic dissociation constants.

^dK_d cannot be determined because of non-hyperbolic binding kinetics.

^e,f Rate constants in the fast and slow phases, respectively, determined at a maximal ligand concentration (18 μM).