Elementary plant Biochemistry and Biotechnology (2+1)

b.Non-competitive inhibitor

Non-competitive inhibitor

•Non-competitive inhibitors bind to a site other than the active site on the enzyme often to deform the enzyme, so that, it does not form the ES complex at its normal rate.
•Once formed, the ES complex does not decompose at the normal rate to yield products.
•These effects are not reversed by increasing the substrate concentration.

E + I → EI
ES + I → ESI

•Some enzymes possessing an essential -SH group are non-competitively inhibited by heavy metal ions (Hg2+, Pb2+).
•Some metalloenzymes are inhibited non competitively by metal chelating agents like ethylene diamine tetraacetic acid (EDTA).
•Inhibitors are used as tools to probe the mechanism of enzyme - catalysed reactions and as therapeutic agents.
•In case of noncompetitive inhibition, Vmax is lowered but Km is not altered

Uncompetitive inhibitor:In case of uncompetitive inhibition, the inhibitor binds only to free enzyme and not to the enzyme substrate [ES] complex.