2. Enzymes
Enzymes can be defined as biological polymers that catalyze biochemical reactions.
Enzymes are proteins comprised of amino acids linked together in one or more
polypeptide chains .
Substrate:
1. The initial stage of metabolic process depends upon enzymes which react with a molecule
and is called the substrate .
Product:
1. Enzyme converts substrate into other distinct molecule which are known as
product.
Ribozyme:
1. Enzymes consist of proteins except in the class of RNA catalyst called ribozyme. The word
ribozyme is derived from the ribonucleic acid enzyme.
2. Many ribozyme are molecules of ribonucleic acid which catalyze reactions in one of their
own bonds or among other RNA ‘s.
3. Enzymes Structure:
Enzymes are actually made up of thousands of amino acids that are linked in a
specific way to form different enzymes.
The enzymes chains fold over to form different enzymes of different shapes
and structures .
1. Primary Structure:
In primary structure there is linear order of amino acids.
Secondary structure:
It refers to the interaction of amino acids in chains which are closely
related.
Tertiary Structure:
It refers to overall folding of the entire polypeptide chain into specific 3D
shape. It is compact globular shaped.
Quaternary Structure:
In this structure multiple polypeptide chains combine into one .
4. Enzymes Classification:
Oxidoreductases:
1. It catalyzes the oxidation reaction where the electron tend to travel from one form
of molecule to other.
Transferases:
1. It helps in the transportation of the functional group among acceptors and donor
molecules.
Hydrolases:
1. They are hydrolytic enzymes which catalyze the hydrolysis reaction by adding water
to cleave the bond and hydrolyze it .
Lyases:
1. It adds water ,carbon dioxide or ammonia across double bonds or eliminate these to
create double bonds.
Isomerases:
1. IT catalyze the structural shifts present in a molecule? Thus causing the change in
shape of molecule.
5. Ligases:
1. Ligases catalyze the association of two molecules. For example, DNA
ligase catalyze joining of two fragments of DNA by forming
phosphodiester bond.
6. Functions of Enzymes:
Enzymes help in signal transduction. The most common enzymes used in
the process include protein kinase that catalyze phosphorylation of
proteins.
They break down large molecules into smaller substances that can be
easily absorbed by body.
They help in generating energy in body. ATP synthase is the enzymes
involved in synthesis of energy.
They are responsible for movement of ions across plasma membrane .
They function to recognize the internal structure of cell to regulate cellular
activities.
7. Factors affecting enzyme activity:
Temperature and pH:
1. The temperature or pH at which a compound show’s it’s maximum activity is
called optimum temperature or pH.
2. A temperature or pH more than optimum may alter the molecular structure of
the enzyme
3. If temperature is increased from optimum temperature the enzymes will
denatured.
Concentration and type of substrate:
1. The chemical that binds to active site of enzyme can inhibit the activity of
enzymes and such substrate is known as inhibitor.
2. Enzymes have saturation points that is once all enzymes added are occupied
by substrate molecules its activity will be ceased.
8. Salt concentration:
1. Changes in salinity adds or removes anions and cations.
2. Disrupts bond and 3D shape
3. Disrupts attraction between charged amino acids
4. Enzymes intolerant of extreme salinity.
9. Co enzymes:
1. An organic molecules that binds to active site of certain enzymes to assist in catalysis of
reaction.
Function:
1. It can function as intermediate carrier of electron during these reactions or be transferred
between enzymes as functional group.
Example:
1. Nicotineamideadinine di nucleotide,flavin adenine di nucleotide.
Co factors:
1. Co factor can be metals or small organic molecules and their primary function is to assist in
enzymes activity.
Types:
1. Inorganic ions
2. Organic molecules known as co enzymes.
Isoenzymes:
1. Multiple forms of same enzyme that catalyze the same chemical reactions.
2. They are produced by single gene and some are produced from more than one gene.
