Qn 6: In competitive enzyme inhibition
True/False


(a) The inhibitor denatures the enzyme


(b) There is a change in the KM of the enzyme for its substrate


(c) The inhibitors usually have analogous structures to the substrates


(d) Vmax can never be attained in the presence of the inhibitor


(e) The inhibitor combines irreversibly with the enzyme.










ans:
a) False Competitive inhibition is readily reversible. Denaturation (unfolding of the polypeptide 3-D structure) would probably be irreversible. The statement is clearly false.

A competitive inhibitor inhibits enzyme activity by competing with substrate for binding to the active site of the enzyme, thereby preventing entry of the substrate into the active site. A competitive inhibitor therefore has structural resemblance to the substrate.

b) True Competitive inhibitors alter KM but not Vmax.


c) True A competitive inhibitor inhibits enzyme activity by competing with substrate for binding to the active site of the enzyme, thereby preventing entry of the substrate into the active site. A competitive inhibitor therefore has structural resemblance to the substrate.


d) False It is a hallmark of competitive inhibition that the addition of excess substrate can overcome the inhibitory effects at a given inhibitor concentration. In other words, the substrate concentration can be raised sufficiently to completely overcome the effects of the inhibitor and therefore allows the enzyme to operate at maximal velocity, i.e. Vmax.


e) False Both competitive and non-competitive inhibition refer to situations where the inhibitor acts reversibly with the enzyme.

If the interaction was irreversible, the effect would not be overcome by increasing the concentration of substrate.