ENZYME:
“Enzymes can be defined as biological polymers that catalyze biochemical reactions.”
The majority of enzymes are proteins with catalytic capabilities crucial to perform different processes.
Metabolic processes and other chemical reactions in the cell are carried out by a set of enzymes that are
necessary to sustain life.
Enzymes are found in all tissues and fluids of the body. Catalysis of all reactions taking place in metabolic
pathways is carried out by intracellular enzymes. The enzymes in the plasma membrane govern the
catalysis in the cells as a response to cellular signals and enzymes in the circulatory system regulate the
clotting of blood. Most of the critical life processes are established on the functions of enzymes.
Enzyme Structure
Enzymes are a linear chain of amino acids, which give rise to a three-dimensional structure. The
sequence of amino acids specifies the structure, which in turn identifies the catalytic activity of the
enzyme. Upon heating, the enzyme’s structure denatures, resulting in a loss of enzyme activity, which
typically is associated with temperature.
Compared to its substrates, enzymes are typically large with varying sizes, ranging from 62 amino acid
residues to an average of 2500 residues found in fatty acid synthase. Only a small section of the structure
is involved in catalysis and is situated next to the binding sites. The catalytic site and binding site
together constitute the enzyme’s active site. A small number of ribozymes exist which serve as an RNA-
based biological catalyst. It reacts in complex with proteins.
Enzymes Classification
Types Biochemical Property
The enzyme Oxidoreductase catalyzes the oxidation reaction where the electrons tend to
Oxidoreductases
travel from one form of a molecule to the other.
The Transferases enzymes help in the transportation of the functional group among
Transferases
acceptors and donor molecules.
Hydrolases are hydrolytic enzymes, which catalyze the hydrolysis reaction by adding
Hydrolases
water to cleave the bond and hydrolyze it.
Adds water, carbon dioxide or ammonia across double bonds or eliminate these to create
Lyases
double bonds.
The Isomerases enzymes catalyze the structural shifts present in a molecule, thus causing
Isomerases
the change in the shape of the molecule.
Ligases The Ligases enzymes are known to charge the catalysis of a ligation process.
Cofactors
Cofactors are non-proteinous substances that associate with enzymes. A cofactor is essential for the
functioning of an enzyme. The protein part of enzymes in cofactors is apoenzyme. An enzyme and its
cofactor together constitute the holoenzyme.
There are three kinds of cofactors present in enzymes:
Prosthetic groups: These are cofactors tightly bound to an enzyme at all times. FAD (flavin
adenine dinucleotide) is a prosthetic group present in many enzymes.
Coenzyme: A coenzyme binds to an enzyme only during catalysis. At all other times, it is
detached from the enzyme. NAD is a common coenzyme.
Metal ions: For the catalysis of certain enzymes, a metal ion is required at the active site to form
coordinate bonds. Zinc is a metal ion cofactor used by a number of enzymes.
MODE OF ACTION:
Four Steps of Enzyme Action
1. The enzyme and the substrate are in the same area. Some situations have more than one
substrate molecule that the enzyme will change.
2. The enzyme grabs on to the substrate at a special area called the active site. The
combination is called the enzyme/substrate complex. Enzymes are very, very specific and don't
just grab on to any molecule. The active site is a specially shaped area of the enzyme that fits
around the substrate. The active site is like the grasping claw of the robot on the assembly line. It
can only pick up one or two parts.
3. A process called catalysis happens. Catalysis is when the substrate is changed. It could be
broken down or combined with another molecule to make something new. It will break or build
chemical bonds. When done, you will have the enzyme/products complex.
4. The enzyme releases the product. When the enzyme lets go, it returns to its original shape. It
is then ready to work on another molecule of substrate.
FACTORS AFFECTING :
Clinical importance of Enzymes
