PHAR 505 Lecture Notes - Lecture 5: Inverse Agonist, Enzyme Kinetics, Dissociation Constant
23 Nov 2017
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A chemical equilibrium reaction can be used to describe r:l interactions. At eq, the rate of complex association is equal to the rate of dissociation. The ratio of the kinetic constants kon and koff is the equilibrium constant, kd. The proportion of receptor or enzyme occupied by a ligand at any given time is called the occupancy: the occupancy determines the potency and efficacy of a drug, remember the concept of spare receptors from 301! The receptor occupancy, y, is related to kd and r and l concentrations. When l concentration = kd r occupancy = 50% The equation describing an inhibitor:receptor (i:r) interaction is the same form as for the l but with the inhibition constant, ki. Reversible competitive inhibitors produce a binding isotherm with an apparent eq constant, kapp: kapp is a function of both the l and i eq constants kl and ki, as well as the.
