Enzymes are biological catalysts, mainly
proteins, generated by an organism to speed up
They can be described as any of several complex
proteins that are produced by cells and act as
catalysts in specific biochemical reactions.
Biological catalysts are those catalysts which are
found in living organisms and they speed up the
metabolic reactions occurring in them.
HISTORY OF ENZYMES
Around late 17th and early 18th centuries, the
digestion of meat by stomach secretions and the
conversion of starch to sugars by plant extracts and
saliva were known. However, the mechanism by which
this occurred had not been identified.
In 1833, French chemist Anselme Payen discovered
the first enzyme, diastase.
In 1877, German physiologist Wilhelm Kühne first
used the term enzyme, which is Greek for "in
leaven", to describe this process. It was later used to
refer to nonliving substances, such as pepsin.
A substance that lowers activation energy of a
reaction so the reaction occurs more quickly but, in
the end, is NOT used up by the reaction is called a
To start any chemical reaction, energy is required.
The minimum amount of energy required to start a
reaction is known as it activation energy.
Activation Energy can be defined as the energy that
must be added to cause molecules to react with one
Metabolism can be described as a set of biochemical
reactions on which the entire life of living organisms
METABOLISM= Anabolism + Catabolism
CATABOLISM: biochemical reactions in which
larger molecules are broken down.
ANABOLISM: biochemical reactions in which larger
molecules are synthesized.
This proves that biochemical reactions
are actually energy transfers.
Importance of Metabolism:
Metabolism is very essential for carrying out all the life
processes as a disturbed metabolic system can result in
severe diseases and retardation.
EXTRACELLULAR AND INTRA
Enzymes that are produced inside cells but work
Enzymes that work inside the cells.
WHAT DO ENZYMES DO?
Some of the ways in which enzymes react are:
Lowering the activation energy by creating suitable
Bringing substrates together in the correct
orientation to react.
It forms ES complex for a while during the reactions.
CHARACTERISTICS OF ENZYMES
Enzymes are globular complex protein structures
made up of long linear chains of amino acid ranging
from just 62 amino acid residues in size to over
Most enzymes are much larger than the substrates
they act on.
Unlike most catalysts enzymes are NOT consumed by the
reactions they catalyze.
During reactions only a small area is directly involved.
This area is called active site.
• It is the region where the substrate is recognized and then bound for
• An enzyme substrate is the material upon which an enzyme acts.
• A product is something "manufactured" by an enzyme from its
There are some enzymes that need additional non
protein molecules/ions called cofactors. Cofactors
can be considered "helper molecules" that assist in
Need cofactors but don’t
4. Metabolic Pathways
When enzymes work together metabolic pathways
are formed. In metabolic pathways a chain or path of
reactions is formed.
Inhibitors are molecules that decrease enzyme activity.
Many drugs and poisons are enzyme inhibitors.
Some types of inhibitors are given here:
Competitive :Substrate and inhibitor compete for
Uncompetitive :The inhibitor cannot bind to the free
enzyme, only to the ES-complex.
Non-competitive : can bind to the enzyme at the
binding site at the same time as the substrate, but not
to the active site.
Activators have the opposite effect on enzymes. They
are the molecules that increase enzyme activity.
WHAT FACTORS AFFECT ENZYMES?
Enzymes are specific about the working conditions
they are provided.
Changes in the working conditions can change the type
of enzyme, its active site or its speed.
Some of the factors affecting enzyme activity are
3. Substrate Concentration
Every enzyme works at its best when given a specific
temperature. This temperature is called the
optimum temperature of that enzyme.
The optimum temperature of human enzyme is
Reactions are accelerated when the temperature
rises to a certain limit .But when this limit is crossed
denaturation of enzymes takes place.
Optimum pH is the range of pH at which enzymes
A slight change in this optimum pH causes:
i).retardation in enzyme activity.
ii).blockage of enzymes.
iii).ionization of amino acids at the active sites.
3. Substrate Concentration
If enzyme molecules are available in a
reaction, increase in substrate concentration causes
increase in the rate of reaction.
If the ratio of enzymes is less than the ratio of
substrates then the enzymes enter a state called
saturation of active sites.
HOW ENZYMES REACT?
Lock and Key Model:
The enzyme and substrate are specific to each other.
The active site of an enzyme fits together with a
substrate like a lock and key. The key is the substrate
and the lock is the enzyme.
Induced Fit Model:
The enzyme is induced to undergo a slight alteration
in order to fit with the substrate perfectly.
USES OF ENZYMES IN DAILY LIFE
Enzymes are produced in living organisms by cells but
the enzymes used for commercial purposes are
synthetic and made in industries.
Enzymes are used in:
1. Bread production.
3. Paper production.
4. Production of cleaning products (detergent etc.)
Some Enzymes And Their Applications
APPLICATION ENZYMES USED
Food processing Amylase,Protease
Baby food Trypsin
Brewing industry Amylase,Protease
Fruit juices Cellulase,Pectinases
Dairy industry Lipases,Lactases
Paper industry Amylase,Ligninase,
Biological detergent Amylase,Lipase,Cellulases
Rubber industry Catalase
Photographic industry Protease