FIGURE 6.

Reaction of wild-type ALAS- and Ser-254 variant-glycine complexes with succinyl-CoA under single turnover conditions. The data for single turnover quinonoid intermediate formation and decay reaction kinetics were fitted with the SIFIT program (OLIS, Inc.). The data (●) are overlaid with the line representing the fitted data. A, rate constants for the three-step sequence in the wild-type enzyme are as follows: 6.0, 2.0, and 0.075 s⁻¹. B, rate constants for the three steps in S254A-catalyzed reaction are as follows: 4.8, 0.8, and 0.19 s⁻¹. C, rate constants for the three steps in S254T-catalyzed reaction are as follows: 1.4, 0.2, and 0.037 s⁻¹.