Figure 10.
Determination of the rate constant of the IspS reaction based on the transients shown in Figure 9. The total DMADP pool size is the integral from the time of darkening (t0) to reaching the baseline level (tf). This DMADP pool size corresponds to the isoprene emission rate at the time of darkening (top inset for the data from Fig. 9A). Integrating backward from time tf to arbitrary time t provides a DMADP pool size that corresponds to the isoprene emission rate at this time t (bottom inset). Thus, for any isoprene emission rate in the dark, we obtained the corresponding pool sizes. For a first-order reaction, a linear dependence is expected between the pool size and the IspS reaction rate. Accordingly, the slope of this dependence provides the rate constant of the IspS reaction. The black symbols correspond to the dark measurements at 33°C (Fig. 9A), while the white symbols correspond to the measurements at 44°C (Fig. 9B). Average isoprene emission rates and rate constants derived from replicate experiments are shown in Figure 5.