. 1997 Feb 18;94(4):1124–1129. doi: 10.1073/pnas.94.4.1124

Table 3.

Kinetic parameters of synthetic mutant DHFRs and inhibition by antifolates Pyr and Cyc

Construct	Kinetic parameter
	k_cat, sec⁻¹	K_m H₂folate, μM	K_m NADPH, μM	k_cat/K_m,^* (M⁻¹·sec⁻¹) × 10⁶	Inhibition by antifolate, K_i, nM
	k_cat, sec⁻¹	K_m H₂folate, μM	K_m NADPH, μM	k_cat/K_m,^* (M⁻¹·sec⁻¹) × 10⁶	Pyr	Cyc
Wild type^†	88	13 ± 5	5 ± 1	6.8	1.5 ± 0.2	2.6 ± 0.3
A16V^‡	1.6	168 ± 14	57 ± 7	0.01	6 ± 1	565 ± 40
N51I^‡	2.6	3.2 ± 0.2	4.0 ± 0.2	0.81	0.4 ± 0.03	4.7 ± 0.2
C59R^‡	122	1.6 ± 0.1	4.4 ± 0.3	76	1.1 ± 0.1	4.7 ± 0.2
S108N^†	92	25 ± 9	7 ± 2	3.7	13 ± 4	15 ± 2
S108T^‡	36	14 ± 2	17 ± 3	2.6	1.4 ± 0.2	1.6 ± 0.2
I164L^‡	33	14 ± 1	15 ± 1	2.4	0.83 ± 0.05	9.0 ± 0.5
A16V + S108T	19	29 ± 2	24 ± 1	0.64	3.6 ± 0.3	2129 ± 100
A16V + S108N^§
N51I + S108N^†	77	6 ± 1	1.9 ± 0.4	13	37 ± 6	24 ± 4
C59R + S108N	4.2	24 ± 1	15 ± 1	0.18	72 ± 3	82 ± 4
N51I + C59R + S108N	3.2	6.2 ± 0.3	10 ± 1	0.53	120 ± 5	103 ± 8
C59R + S108N + I164L	3.0	18 ± 1	36 ± 3	0.17	383 ± 33	1141 ± 98
N51I + C59R + S108N + I164L	15	14 ± 1	25 ± 6	1.1	859 ± 117	730 ± 19

Calculated from K_m values for H₂folate.

^†

Data from ref. 19.

^‡

Not found in nature.

^§

No DHFR activity detected and not found in nature.