enzyme specificity

                                                      Enzyme Specificity

Enzymes are proteins that catalyse reactions

Enzyme Specificity

Enzymes show five types of specificity.

1. Relative, low or bond specificity
2. Moderate, structural or group Specificity
3. Absolute, high or substrate specificity
4. Optical or Stereospecificity
5. Dual Specificity       

Relative, Low or bond specificity

 Enzymes act on substrate that are similar in structure and contain same type of bonds.

e.g 

       Amylase acts on α-1-4 glycosidic bonds in starch, dextrin and glycogen

       lipase hydrolyses ester bonds in triglycerides.

Moderate, structural or group specificity

enzyme is specific not only to bond but also structure surrounding it.

e.g

      Pepsin is an endopeptidase that hydrolyses central peptide bond in which amino group belongs to aromatic amino acids

     Trypsin is an endopeptidase that hydrolyses central peptide bond in which amino group belongs to basic amino acids

Absolute, high or substrate specificity

enzyme acts only on one substrate

e.g

      Uricase acts only on Uric acid

      Lactase acts only on Lactose

Optical or stereospecificity

enzyme is specific to substrate but also to its optical configuration.

e.g

     D-amino acid oxidase acts only on D-amino acids

     β-Glycosidase acts only on β-glycosidic bonds that are present in cellulose

Dual specificity

It has two types.

• enzyme acts on two substrates for same kind of reaction. For example Xanthine oxidase acts on hypoxanthine and xanthine.
• enzyme acts on one substrate for two kinds of reactions. For example isocitrate dehydrogenase acts on isocitrate by oxidation followed by decarboxylation.