Figure 4.
Kinetics of a pre-steady-state burst of ALA product in the 2XALAS reaction. 2XALAS (8.6 μM) (filled circles) preincubated with glycine (200 mM) was quickly reacted with succinyl-CoA (150 μM) at 20°C. The concentrations shown in parentheses are final concentrations after mixing. The reactions were quenched with perchloric acid (0.14 M) at various aging times, and the ALA concentration was determined. The curve represents the best fit to Equation 4 with a burst amplitude of 8.52 ± 0.30 μM, a burst rate of 48.6 ± 6.1 sec−1, and a steady-state rate of 0.09 ± 0.01 sec−1. For comparison, the time course for the reaction of ALAS (30 μM) (open triangles) preincubated with glycine (200 mM) with succinyl-CoA (150 μM) at 20°C is included (from Zhang and Ferreira 2002).