1. Enzymes are protein catalysts that enhance the rate of biochemical reactions by lowering their activation energy. They were first discovered in 1833 by Payne and have been extensively studied since.
2. Enzymes are classified based on the type of reaction they catalyze and have a systematic naming system using EC numbers. They interact with substrates using either the lock and key or induced fit models.
3. Enzymes have many applications including in medicine, industry, food production, and biofuels. They are used as diagnostic tools, in manufacturing processes, and to convert biomass into fuels.
3. ENZYME
• Enzymes are usually protein that act as biocatalyst, which enhances the
rate of biological reactions to several thousand to million folds by
lowering its activation energy.
4. Discovery and History of Enzymes
• 1833: Payne found that an alcohol precipitate of a malt extract contained a
substance that converted starch into sugar. This was the first discovery of
an enzyme and named it diastase.
• 1850: Louis Pasteur observed that ferment of sugar into alcool by yeast is
catalysed by ferments (later named enzymes).
• 1876: W.F. Kuhne coined the term enzyme (Greek, which means ‘in
yeast’).
5. • 1894: Emil Fischer performed some classical studies on carbohydrate
metabolizing enzymes in which he demonstrated the specificity
shown by an enzyme for its substrate. And proposed the lock and key
hypothesis
• 1897: Edward Buchner succeded in extracting the set of enzymes
from the yeast cells in active form and demonstrated for the first time
the conversion of sugar into alcohol in vitro.
• 1926: J.B. Sumner isolated, purified and also successfully crystallized
the enzyme urease from jack beans. He found that the urease crystals
are purely made of proteins and hence reported that enzymes are
nothing but proteins.
6. • 1930: John Northrop and his colleagues crystallized pepsin and
trypsin and found that they were also proteins crystals. Received
Nobel Prize in 1935.
• 1958: The induced-fit model was proposed by Daniel Koshland.
• 1964: R.B. Merrifield and his group paved the way for laboratory
synthesis of enzymes for the first time (tailor made synthetic enzymes
called Synzymes. The first enzyme which was assembled on a solid
phase matrix was the Ribonuclease
• 1965: Lysozyme was the first enzyme for which the X-ray structure
was determined at high resolution by David Phillips
7. • 1962 : W. Arber discovered restriction enzymes.
• 1986: The belief that ‘All enzymes are proteins but all proteins are not
enzymes’ was shattered by Alexander Rich and Thomas Cech’s group
discovered that certain RNA molecules also exhibited catalytic properties
like enzymes (Ribozymes).
• 1996: Site- directed mutagenesis technique was developed by M.Smith.
8. Properties of Enzyme
• All enzymes are proteins which act as biocatalyst except Ribozyme.
• They catalyse that rate of biochemical reactions.
• They have the enormous power of catalysis.
• Enzymes are highly specific for their substrate.
• Enzyme posses active site at which interaction with substrate take
place.
• Enzyme lowers the activation energy.
• Enzyme themselves do not undergo any chemical change but are
regenerated at th end of reaction.
9. Classification
S.NO CLASS REACTION
CATALYZE
EXAMPLE
1 Oxidoreductases Oxidation & Reduction
Reaction
Pyruate Dehydrogenase
2 Transferases Atom/Group Transfer Transaminase
3 Hydrolases hydrolysis Pepsin
4 Lyases Group removal Aldolase
5 Isomerases Isomerization Phosphoglucomutase
6 Ligases Joning of molecules DNA ligase
10. Nomenclature
• It is done by : Adding a suffix to the enzyme name. The suffix comes from
either the substrate it acts on or from its catalytic action.
Eg: Urease catalyzes hydrolysis of Urea
• IUBMB has adopted a systematic method of naming a enzyme.
Uses a four-component number (the EC number)
Identifies an enzyme in terms of reaction catalysed.
•Six recognized groups of enzymes:
Oxidoreductases (EC 1),
11. Transferases (EC 2)
Hydrolases (EC 3)
Lyases (EC 4)
Isomerases (EC 5)
Ligases (EC 6).
•Each enzyme is characterized by a code no. called Enzyme Code no.
or EC number and contain four Figure (digit) separated by a dot.
•First digit represents the class, Second digit stands for subclass, Third
digit stands for the sub-sub class or subgroup, Fourth digit gives the
serial number of the particular enzyme in the list.
•Example: EC 2. 7. 1. 1 for hexokinase
12. Models
There are two models used to describe the way enzymes interact with
substrates:
The 'lock and key’ model
The ‘induced fit’ model
13. Lock and Key Model
• According to Emil Fischer(1894 ) the enzyme’s active site
complements the substrate precisely like the lock and key.
• The substrate fits a particular active site like a key fits into a
particular lock
• This theory of enzyme-substrate interaction explains how
enzymes exhibit specificity for a particular substrate
14. Induced Fit Model
• According to Daniel Koshland (1958), the enzyme’s active site is not a
completely rigid fit for the substrate
•Instead, the active site will undergo a conformational change when
exposed to a substrate to improve binding
15. Mechanism of enzyme catalysis
• An enzyme attracts substrates to its active site, forming enzyme-
substrate complex and catalyzes the chemical reaction by which
products are formed, and then allows the products to dissociate
(separate from the enzyme surface)
Step 1: Binding of substrate to enzyme to form activated complex.
E + S → ES
Step 2: Decompostion of the activated complex to form product.
ES → E + P
16.
17. Enzyme action by lowering activation energy
• The graph shows how the activation
energy is lowered in the presence of an
enzyme (blue line).
• The transition state is usually the most
unstable part of the reaction since it is the
one with the highest free energy.
• Enzymes (blue line) change the formation
of the transition state by lowering the
energy and stabilizing the highly
energetic unstable transition state. This
allows the reaction rate to increase.
18. Factors affecting enzyme activity
1. Temperature: Raising
temperature generally
speeds up a reaction, and
lowering temperature slows
down a reaction. However,
extreme high temperatures
can cause an enzyme to
lose its shape (denature)
and stop working.
19. 2. pH: Each enzyme has an
optimum pH range. Changing the
pH outside of this range will slow
enzyme activity. Extreme pH
values can cause enzymes to
denature.
3. Enzyme concentration:
Increasing enzyme concentration
will speed up the reaction, as long
as there is substrate available to
bind to. Once all of the substrate is
bound, the reaction will no longer
speed up, since there will be
nothing for additional enzymes to
bind to.
20. 4. Substrate concentration: Increasing
substrate concentration also increases
the rate of reaction to a certain point.
Once all of the enzymes have bound,
any substrate increase will have no
effect on the rate of reaction, as the
available enzymes will be saturated and
working at their maximum rate.
5. Inhibitors: Enzyme inhibitors are
compounds which modify the catalytic
properties of the enzyme and, therefore,
slow down the reaction rate, or in some
cases, even stop the catalysis. Inhibitors
work by blocking or distorting the active
site.
21. Application
Medical Enzymes
(a)Diagnostic enzymes : Arginase for L-arginine levels in plasma and urine
(b) Biosensors : Glucose oxidase in Glucometer
(C)Therapeutic Enzymes : Streptokinases to lyse blood clot
Industrial Applications
(a)Pharmaceutical industry: Production of insulin uses Restriction enzyme.
(b) Food and brewing industry: α-Amylase and glucoamylase enzymes are
added to improve quality of food.
22. (c) Paper and pulp industry : Cellulases, hemicellulases and
pectinases have been used in paper and pulp industry
(d) Agriculture industry: Phytate is hydrolyse by Phytases (substrate
rich in phosphorus, Calcium and other minerals)
Biofuel:
Enzymes converts grains into fuel ethanol, plus enzymes that assist the
conversion of biomass for cellulosic ethanol. lipases (triglyceride
hydrolases) are mainly used for biodiesel production.
23. Refferences :
• Dumorné K, Córdova DC, Astorga-Eló M, Renganathan P.
Extremozymes: A Potential Source for Industrial Applications. J
Microbiol Biotechnol. 2017 Apr 28;27(4):649-659. doi:
10.4014/jmb.1611.11006. PMID: 28104900.
• Tao, Z., Dong, B., Teng, Z., & Zhao, Y. (2020). The classification of
enzymes by deep learning. IEEE Access, 8, 89802-89811.
• http://biochem.du.ac.in/web/uploads/45%20Enzymes%20-
%20Applications.pdf
