Bisubstrate Inhibition:  Theory and Application to N-Acetyltransferases

Bisubstrate inhibitors represent a potentially powerful group of compounds that have found significant therapeutic utility. Although these compounds have been synthesized and tested against a number of enzymes that catalyze sequential bireactant reactions, the detailed theory for predicting the expected patterns of inhibition against the two substrates for various bireactant kinetic mechanisms has, heretofore, not been presented. We have derived the rate equations for all likely sequential bireactant mechanisms and provide two examples in which bisubstrate inhibitors allow the kinetic mechanism to be determined. Bisubstrate inhibitor kinetics is a powerful diagnostic for the determination of kinetic mechanisms.