Elementary plant Biochemistry and Biotechnology (2+1)

Specificity of the enzymes

• One of the characteristic feature which distinguishes enzymes from catalysts is their specificityEnzymes are specific in the reaction catalysed and in their choice of substrates.
• It usually catalyses a single chemical reaction or a set of closely related reactions.
• Three kinds of specificities are observed

1. Absolute specificity

• When enzymes catalyse only one particular reaction they are said to exhibit absolute specificity.e.g. Urease acts only on urea.

2. Group specificity

• Enzymes acting on a group of substances that possess a particular type of linkage common to that group of substances are said to exhibit group specificity.
• Amylase hydrolyses the group of substances like starch, dextrin and glycogen, which have the same type of glycosidic linkages (α1,4).

3.Optical specificity

• Almost all enzymes show a high degree of optical specificity.
• There are certain enzymes which catalyse the hydrolysis of same group of substances possessing same optical activity.
• Eg. D-amino acid oxidase acts on D-amino acid and L-amino acid oxidase acts on L-amino acid. Maltase catalyses the hydrolysis of α-but not β- glycosides.