The effect of Pi on the apparent rate constant . To deduce the rate and association constants of steps 4 and 5, the results of Figure 7 were fitted to (6). The MgATP concentration was kept at 5 mM. The continuous lines are based on (6) with best-fit parameters. of (7) was calculated based on the and obtained from the MgATP study (Table 5) and at  mM.