Table 2.

Data and constants relating to the dimer to monomer dissociation equilibrium of DHODA

	Native DHODA	E206K-K296E mutant DHODA	E206K-K296E mutant DHODA with 0.15 M NaCl
Ao (U/mg)a	28.5	29.3	26.2
Ar (U/mg)a	13.0	13.6	11.1
[Enzyme]totala (μM)	0.098	9.76	0.976
[Dimer]a (μM)	0.0218	2.26	0.212
[Monomer]a (μM)	0.0519 (0.0745)	5.24 (7.11)	0.562 (0.867)
KDa (μM)	0.123 μM (0.25 μM)	12 μM (22 μM)	1.49 μM (3.7 μM)
k+1b (min−1)	0.024 ± 0.002	0.091 ± 0.003	0.026 ± 0.002
KDc (μM)	0.26 ± 0.05	37 ± 22	3.5 ± 0.6
k−1d (μM−1 min−1)	0.043	0.0010	0.0027

^a The total enzyme concentrations is given as monomers. The data are taken from the decay experiments shown in Fig. 2 ▶. Monomer and dimer concentrations and the K_D values are calculated as explained in Materials and Methods. The values of [Monomer] and K_D in parentheses were calculated by assuming an identical initial specific activity. A_o = 35 U/mg in all cases.

^b k₊₁ is assumed to be equal to k_obs for the most dilute enzyme samples.

^c Obtained from the data in Fig. 3 ▶ by eq. 3.

^d Association rate constant derived by division of k₊₁ with K_D above.