Enzyme specificity definition
Definition of enzyme substrate specificity and different types of enzyme
specificity. bond specificity, Group specificity, substrate specificity,
stereo specificity, optical specificity, geometrical specificity, cofactor
Enzymes are biological catalysts. They accelerate the rate of metabolic
reactions in the cells by reducing the activation energy of the reactants.
Almost all enzymes are specialized proteins with definite structural
conformations. Important characteristic features of enzyme are:
1. Catalytic Power (ratio of enzyme catalyzed rate of a reaction to
the un-catalyzed rate)
2. Regulation (control of enzymatic reaction)
3. Specificity (Selectivity of enzyme to their substrate)
Specificity is the ability of an enzyme to choose exact substrate from a
group of similar chemical molecules. The specificity is actually a
molecular recognition mechanism and it operates through the structural and
conformational complementarity between enzyme and substrate. Enzymes show
different degrees of specificity towards their substrate.
The specificities shown by enzymes are grouped into 6 categories
1. Bond specificity
2. Group specificity
3. Substrate specificity
4. Stereo specificity (Optical specificity)
5. Geometrical specificity
6. Co-factor specificity
Bond specificity is also called as relative specificity. Enzymes showing
bond specificity are specific to substrates having similar bonds and
It is also called moderate specificity. Here the enzyme is specific to a
bond and groups surrounding the bonds. Group specificity is more than that
of bond specificity. Endopeptidases and exopeptidases (two general classes
of proteinases) are classical examples for group specificity.
Substrate specificity is also called as absolute specificity, since here
the specificity is very high. Enzymes showing substrate specificity are
specific only to one substrate and one reaction.
Optical specificity of enzyme is also called as stereo-specificity. Here
the enzyme is specific not only to substrate but also to its optical
configuration. Optical specificity of enzyme is considered as the highest
specificity shown by any class of enzyme in the living world.
In geometrical specificity, single enzyme can act on different substrates
having similar molecular geometry and hence here specificity is very less.
Example: Alcohol dehydrogenase can oxidize both ethanol and methanol to
yield corresponding aldehydes since both these alcohols have similar
(6). Co-factor specificity
Co-factors are non-protein part of enzyme required for the functioning of
some enzymes. Enzyme which requires co-factors for their activity shows
co-factor specificity. Only correct combination of substrate and co-factor
allows enzymatic reaction. In the absence of specific co