Table 3.

Rate constants and kinetic parameters for the reaction of KYN with HsKYNase_93D9 and HsKYNase_66 derived by the global fitting of the experimental data (Fig. 2a, d) to the kinetic models shown in Fig. 2b and e

Rate constant and kinetic parameter	HsKYNase_93D9		HsKYNase_66
	Best fit	95% Confidence interval	Best fit	95% Confidence interval
k1	0.24 μM−1s−1	(0.22, 0.27)	5.9 μM−1s−1	(5.5, 6.4)
k−1	4 s−1	(3.31, 4.83)	268 s−1	Locked
k2	0.79 s−1	0.77, 0.81)	3.1 s−1	(2.78, 3.28)
k−2	a0.34 s−1	Locked	19 s−1	Locked
k3	11.5 s−1	Locked	21 s−1	(17.5, 24.8)
k−3	0.001 μM−1s−1	Locked	0.001 μM−1s−1	Locked
k4	11 s−1	Locked	1.5 s−1	Locked
k−4	0.02 μM−1s−1	Locked	0.001 μM−1s−1	Locked
kcat (s−1)	0.68	-	0.75	-
KM (μM)	17.5	-	21.1	-
kcat/KM (M−1s−1)	3.9 × 104	-	3.6 × 104	-

^aRate constants shown in bold font were locked at the displayed value corresponding to either their lower or upper limit during the global fitting process.

Rate constants that were allowed to float during the global data fitting (shown in green font in Fig. 2b and e) are summarized with confidence intervals by contour analysis. Using Eqs. 3, 4 and 5 (Methods) and the rate constants from the pre-steady-state analysis that are listed above, the steady-state kinetic parameters k_cat, K_M and k_cat/K_M were estimated respectively.