Question

12. Uncompetitive inhibitors DO NOT change the following parameters of the targeted enzyme

a) Km

b) Vmax

c) Vmax/Km

d) all of the above

Answer 1

Uncompetitive inhibitors do not change the Vmax/Km value only. It decreases both the Km and Vmax value at a same rate. So, the Vmax/Km value remains constant.

Here is an analytical representation to this. The actual Lineweaver-Burk Equation is

1/v = Km/ Vmax [S] + 1/vmax , [S] = substrate concentration

But in the presence of an uncompetitive inhibitor produces a Y-intercept factor in the graph between 1/ [S] and 1/v. And this Y-intercept term is [I]/Ki. So the new equation now is,

1/v = Km/Vmax[S] + {1+[I]/Ki}/Vmax ,

[I] = Concentration of the inhibitor and Ki = Inhibition constant

Here both the Vmax and Km values increases at a same rate. Hence the Vmax/Km value DOES NOT change.