Specificity of Enzymes

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Specificity of Enzymes

Specificity of Enzymes - Enzymes show striking specificity. They catalyse specific reactions of specific substrates.

Some enzymes are so specific that they catalyse only one type of substrate molecule.

The specificity may extend to only one isomer of a substrate.

The enzyme chymotrypsin catalyses the hydrolysis of acetyl-L-phenyl-alanine methyl ester, but is inert to the D isomer.

The specificity of an enzyme for a sub substrate is the result of stereo chemical complementary attachment between the enzyme and the substrate to form the enzyme substrate complex.

This was originally referred to as the lock and key hypothesis.

It has, however, been shown that the enzyme does riot have a rigid structure but undergoes conformational changes to accept the substrate.

This has been termed induced fit. Substrates are relatively small as compared to the enzyme.

For example the enzyme chymotrypsin contains 249 amino acid residues, while the size of the substrate corresponds to a peptide with two amino acid residues.

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