Introduction
- Enzymes are commonly proteinaceous substances
which are capable of catalysing chemical
reactions of biological origin without themselves
undergoing any change. Therefore, they are called
biocatalysts. A cell with an average diameter of
20 pm has about 1000 chemical reactions going on
at any time. All of them require specific enzymes.
All the enzymes are not present at all the times in
the cell but they are formed as and when required
from the blue print present in DNA. Table shows
examples of some enzymes. - The term ‘enzyme’ was coined by Kuhne (1878)
for catalytically active substances previously
called ferments. Enzymes were actually found out
by Buchner (1897) with the accidental discovery
that fermentation of sugar is not only caused
by living yeast cells but also yeast extract.The
extract obviously possessed biocatalysts required
for the process. Buchner (1903) also isolated the
first enzyme. He was awarded Nobel Prize in the
same year, 1903.
By: SHWETHA .S (Mysore)
Modes of Enzyme Action:
Enzyme-catalysed reactions occur in at least two
steps:
(i) In the first step, an enzyme molecule (E) and the
substrate molecule or molecules (S) collide and
react to form an intermediate compound called
the enzyme-substrate (E–S) complex.
(This step is reversible because the complex can
break apart into the original substrate or substrates
and the free enzyme.)