Elementary plant Biochemistry and Biotechnology (2+1)

a.Competitive inhibitor

Competitive inhibitor

•Any compound which possessess a close structural resemblance to a particular substrate and which competes with that of substrate for the same active site on the enzyme is called as competitive inhibitor.
•The inhibitor is not acted upon by the enzyme and so remains bound to the enzyme preventing the substrate to bind.
•This is a reversible process.
•It depends upon the relative concentration of substrate and inhibitor.
•Competitive inhibition can be completely reversed by addition of large excess of substrate
high inhibitor concn.
E + I → E I
←
high substrate concn.

Eg. the enzyme, succinate dehydrogenase converts succinate to fumarate.
For this reaction, malonic acid is a competitive inhibitor as it structurally resembles that of succinate

•In case of competitive inhibition, Km is increased but Vmax is not altered.