Binding between thermolysin and its specific inhibitor, phosphoramidon.

Equilibrium and kinetic studies on the interaction between thermolysin (E) and its specific inhibitor (I), phosphoramidon (N-(alpha-L-rhamnopyranosyloxyphospho)-L-leucyl-L-tryptophan), have been made by steady-state inhibitory kinetics analysis, fluorometric titration and the stopped-flow method. The inhibitor constant, K1, the dissociation constant of the El complex, Kd, directly obtained by fluorometric titration, and the apparent second-order association constant, kon, obtained with the stopped-flow method are very similar to those for talopeptin (Kitagishi, K., et al. (1983) J. Biochem. 93, 47-53 and 55-59), whose molecular structure differs from that of phosphoramidon only in the configuration of the OH group at the C-4 atom of the sugar moiety. The result suggested that the OH group is not essential for the binding to thermolysin.