Question

1) You are working to design an inhibitor of a viral enzyme that is key for the viral genome replication, as a potential antiviral drug. The laboratory characterization of the enzyme renders the following MM kinetic parameters: K_M=0.5 mM, and k_cat=10⁵ s^-1. The concentration of this enzyme inside infected cells is about 10^-5 And, you know that to be effective in stopping infection the inhibitor needs to decrease the catalytic efficiency of this enzyme by 100 fold.

(a) what would be the best type of inhibition to achieve this result using a single inhibitor (rationalize the answer)?

(b) if the inhibitor has a K_I=K_I’=1 microM, what concentration of inhibitor will you need to achieve this result?

Answer 1

a) In this mixed inhibition will be achieved by using a single inhibitor. It is a type of inhibition of enzyme in which the inhibitor will bind to the enzyme whether or not enzyme has already bound to the substrate has a greater affinity for one state or other.As it can be seen as a mixture of both competitive and uncompetitive inhibition in which the inhibitor can only bind the enzyme if substrate has not already bound and in which inhibitor can only bind the enzyme if substrate has already bound called uncompetitive. In this, the inhibitor binds to the allosteric site that is different than active site where substrate binds. It can result in two type: i) decrease in apparant affinity of enzyme for the substrate, it closely mimics competitive binding (K^app_m> K_m) and ii) increase in apparant affinity of enzyme for substrate that closely mimics uncompetitive binding (K^app_m < K_m).

b) If the Inhibitors has KI=KI'=1 microM, non-competitive inhibition occurs. In this enzyme inhibition where inhibitor reduces activity of enzyme and binds equally to the enzyme whether or not it has already bound the substrate. It can occur when equal amount of inhibitors and substrate are at equal amount.