Covalent inhibitors typically follow a two-step kinetic mechanism characterized by an equilibrium dissociation constant (Ki) for the non-covalent E:I complex and an inactivation rate constant (kinact) to form the covalent E-I complex, Figure .(a). Reversible covalent inhibitors differ from irreversible inhibitors in that the step leading to the formation of the final covalent E-I complex is not permanent.