It is known that Km = (k2 + k-1)/(k1) and Kd = (k-1)/(k1) for a simple unimolecular conversion of E + S ---> ES -----> E + P, but what about the relationship for an ordered sequential bi bi reaction:

E + A ---> EA + B ----> EAB ----> EPQ -----> E + P + Q

I recently discovered the Km for substrate A = 25 uM, but the Kd for substrate A = 660 nM. Is there an equation to make sense of this large difference utilizing the microscopic rate constants?

Thanks!