Impact of mechanism-based enzyme inactivation on inhibitor potency: implications for rational drug discovery

J Pharm Sci. 2000 Nov;89(11):1404-14. doi: 10.1002/1520-6017(200011)89:11<1404::aid-jps4>;2-#.


Mechanism-based enzyme inactivators (MBEIs) have unique kinetic actions that make predictions of potency, selectivity, and potential for metabolic drug interactions more complex than for competitive antagonists. We have derived a mathematical relationship that links the influence of substrate concentration and binding constant ([S] and K(m), respectively), inhibitor concentration and binding constant ([I] and K(I), respectively), and inactivation rate constant (k(inact)) to enzyme activity (v) and maximal activity (V(max)) at any time (t). The kinetic behavior of this relationship was validated in murine-macrophage cell cultures using MBEIs of nitric oxide synthase (NOS). This initial equation was also used in the derivation of a new relationship that directly links the kinetic parameters of mechanism-based inactivation to inhibitory potency at a particular time (IC((t))(50)). Using this direct relationship, we observed that the predicted rank inhibitory potency of a series of MBEIs was improved over that predicted by the K(I) parameter alone. These relationships offer a fundamental understanding of the kinetics of MBEI action and may be useful in the evaluation of these compounds during the discovery process.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Drug Design*
  • Enzyme Inhibitors / pharmacokinetics*
  • Models, Chemical*
  • Nitric Oxide Synthase / metabolism*
  • omega-N-Methylarginine / pharmacokinetics*


  • Enzyme Inhibitors
  • omega-N-Methylarginine
  • Nitric Oxide Synthase