Biochemistry & Molecular biology suject, Created by Asad Chowdhury. University of Dhaka · Department of Pharmaceutical Chemistry.

1. Enzyme

2. Enzyme
Enzymes are proteinous substances that catalyze
hundreds of stepwise reactions that
- Degrade nutrient molecules,
- Conserve and transform chemical energy,
- Make biological macromolecules from simple
precursors.

3. History of Enzyme
- First recognized and described in the late 1700s, in studies
on the digestion of meat by secretions of the stomach
- In the 1850s, Louis Pasteur concluded that fermentation of
sugar into alcohol by yeast is catalyzed by “ferments.” He
postulated that these ferments were inseparable from the
structure of living yeast cells
- In 1877, German physiologist Frederick W. Kühne called
these molecules enzymes.
- Then in 1897 Eduard Buchner discovered that yeast
extracts could ferment sugar to alcohol, proving that
fermentation was promoted by molecules that continued
to function when removed from cells. He named the
enzyme that brought about the fermentation of sucrose
“zymase”.

4. History of enzyme
- In 1907, he received the Nobel Prize in Chemistry for his
biochemical research and his discovery of cell-free
fermentation".
- The isolation and crystallization of urease by James
Sumner in 1926 provided a breakthrough in early enzyme
studies.

5.  Properties of enzyme:
- Enzymes are the most remarkable and highly specialized
proteins: Enzymes, like other proteins, have molecular
weights ranging from about 12,000 to more than 1 million.
- Enzymes have extraordinary catalytic power, often far
greater than that of synthetic or inorganic catalysts.
- They have a high degree of specificity for their substrates,
- They accelerate chemical reactions tremendously
- They function in aqueous solutions under very mild
conditions of temperature and pH.

6. Classification of enzymes
No. Class Types of reactions catalyzed
1 Oxidoreductases Transfer of electrons (hydride
ions or H atoms)
2 Transferases Group transfer reactions
3 Hydrolases Hydrolysis reactions (transfer of
functional groups to water)
4 Lyases Addition of groups to double
bonds, or formation of double
bonds by removal of groups
5 Isomerases Transfer of groups within
molecules to yield isomeric forms
6 Ligases Formation of C-C, C-S, C-O, and
C-N bonds by condensation
reactions coupled to ATP cleavage

7.  How does enzyme work?
Active site & substrate

8. Mechanisms
- Lowering the activation energy
- Lowering the energy of the transition state
- Providing an alternative pathway.
- Reducing the reaction entropy change by bringing
substrates together in the correct orientation to react.
- Increases in temperatures speed up reactions.

9. Enzyme Kinetics

12. Double reciprocal/Lineweaver-Burk plot

13. Inhibition of Enzyme
1. Reversible inhibition:
a. Competitive inhibition
b. Uncompetitive inhibition
c. Mixed inhibition
(a)
(b)
(c)

14. Inhibition of Enzyme
2. Irreversible inhibition: Inhibition of COX by aspirin

15. Kinetics Tests for determining Inhibition Mechanism
The double-reciprocal plot offers an easy way of determining
whether an enzyme inhibitor is competitive, uncompetitive,
or mixed.

16. Kinetics Tests for determining Inhibition Mechanism

17. Control of enzyme activity
1. Enzyme production (transcription and translation of
enzyme genes) can be enhanced or diminished by a cell in
response to changes in the cell's environment. For
example, antibiotics (penicillin) resistance due to
beta-lactamases. Drug interaction.
2. Enzymes can be compartmentalized, with different
metabolic pathways occurring in different cellular
compartments. For example, fatty acids are synthesized
by one set of enzymes in the cytosol, endoplasmic
reticulum and the Golgi apparatus and used by a different
set of enzymes as a source of energy in the mitochondrion,
through beta-oxidation.

18. 3. Enzymes can be regulated by inhibitors and activators.
Negative feedback mechanism can effectively adjust the rate
of synthesis of intermediate metabolites according to the
demands of the cells.
4. Enzymes can be regulated through post-transcriptional
modification. For example, in the response to insulin, the
phosphorylation of multiple enzymes, including glycogen
synthase, helps control the synthesis or degradation of
glycogen and allows the cell to respond to changes in blood
sugar.
5. Some enzymes may become activated when
localized to a different environment (e.g. from a reducing
(cytoplasm) to an oxidizing (periplasm) environment, high
pH to low pH etc.). For example, hemagglutinin in the
influenza virus is activated by a conformational change
caused by the acidic conditions, these occur when it is taken
up inside its host cell and enters the lysosome.

19. Cofactor, Coenzyme:
Some enzymes require no chemical groups for activity other
than their amino acid residues. Others require an additional
chemical component called a cofactor—either one or more
inorganic ions, such as Fe+2, Mg+2, Mn+2 , or Zn+2, or a
complex organic or metalloorganic molecule called a
coenzyme (which are released from the enzyme's active site
during the reaction).
A coenzyme or metal ion that is very tightly or even
covalently bound to the enzyme protein is called a
prosthetic group.
A complete, catalytically active enzyme together with its
bound coenzyme and/or metal ions is called a holoenzyme.
The protein part of such an enzyme is called the apoenzyme
or apoprotein.

20. Cofactor Enzyme
Cu+2
Fe+2 or Fe+3
K+1
Mg+2
Mn+2
Mo
Zn+2
Cytochrome oxidase
Cytochrome oxidase, catalase,
peroxidase
Pyruvate kinase
Hexokinase, glucose 6-
phosphatase, pyruvate kinase
Arginase, ribonucleotide reductase
Dinitrogenase
Carbonic anhydrase,

21. Coenzyme Examples of
chemical group
transferred
Dietary precursor in
mammals
Biocytin
Coenzyme A
Thiamine
pyrophosphate
Pyridoxal
phosphate
Flavin adenine
dinucleotide
Tetrahydrofolate
CO2
Acyl group
Aldehyde
Amino groups
Electrons
One-carbon
group
Biotin
Pantothenic acid and
other compounds
Thiamine (Vitamin B1)
Pyridoxin (Vitamin
B6)
Ribaflavin (Vit B2)
Folate

22. Enzymes and Diseases:
One example is the most common type of phenylketouria.
A mutation of a single amino acid in the enzyme
phenylalanine hydrolase, which catalyzes the first step
in the degradation of phenylalanine, results in build-up
of phenylalanine and related products. This can lead to
mental retardation if the disease is untreated.

23. Industrial Application of Enzymes:
- Food processing
- Baby food preparation
- Brewing industry
- Dairy industry
- Starch industry
- Paper industry
- Biofuel industry
- Rubber industry
- Molecular biology