1. A
Report on
Enzymes
By
Sanjay Jagarwal
(10112047)
Chemical B.tech 3rd year

2. Enzyme Action
Enzymes: proteins that function as biological catalysts.
Catalyst: a substance that speeds up a chemical reaction and
is not changed by the reaction.
Specificity:Enzymes are usually very specific as to
Which reaction they catalyze.
Highly specific Enzymes follows "proof-reading"
mechanisms

3. “Lock and key” model
However certain substances can bind to the enzyme at sites other than the
Active site and modify its activity (inhibitors/co-factors)
Idea that the enzyme is flexible.

4. Induced Fit
This model proposes that the initial interaction between enzyme
and substrate is relatively weak, but that these weak interactions
rapidly induce conformational changes in the enzyme that
strengthen binding.

5. Enzyme reactions
enzyme + productenzyme-substrate complex
E +PES
enzyme + substrate enzyme-substrate complex
E +S ES

6. Mechanisms
Enzymes can act in several ways, all of which lower ΔG‡
(Gibbs energy):
• Lowering the activation energy by creating an
environment in which the transition state is stabilized
• Lowering the energy of the transition state, but
without distorting the substrate.
• Providing an alternative pathway.
• Reducing the reaction entropy change by bringing
substrates together in the correct orientation to
react.

7. Enzyme activity
Four Variables
Temperature
pH
Enzyme Concentration
Substrate Concentration

8. RateofReaction
Temperature

9. RateofReaction
Temperature
0 20 30 5010 40 60

10. RateofReaction
Temperature
0 20 30 5010 40 60
40oC - denatures
5- 40oC
Increase in Activity
<5oC - inactive

11. Effect of heat on enzyme activty
If you heat the protein above its optimal temperature
bonds break
meaning the protein loses it secondary and tertiary structure

12. Effect of heat on enzyme activty
Denaturing the protein

13. Effect of heat on enzyme activty
Denaturing the protein
ACTIVE SITE CHANGES SHAPE
SO SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme can’t regain its correct shape

14. pH effect:
• The ph scale measures how acidic or alkaline a
substance is.
• The chemical properties of many solutions enable
them to be divided into 3 categories:
1) Neutral: solutions with a ph of 7.
2) Alkaline: solutions with a ph greater than 7
3) Acidic: solutions with a ph less than 7.

15. pH scale

16. RateofReaction
pH

17. RateofReaction
pH
1 3 42 5 6 7 8 9

18. RateofReaction
pH
1 3 42 5 6 7 8 9
Narrow pH optima

19. RateofReaction
pH
1 3 42 5 6 7 8 9
Narrow pH optima
WHY?

20. RateofReaction
pH
1 3 42 5 6 7 8 9
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at active
site

21. RateofReaction
Enzyme Concentration

22. RateofReaction
Enzyme Concentration
Enzyme Concentration

23. RateofReaction
Substrate Concentration

24. RateofReaction
Substrate Concentration
Substrate Concentration

25. RateofReaction
Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover

26. METABOLISM
• Metabolism is the sum of all biochemical
reactions occurring in living cells.
• These reactions can be divided into two main
groups:
– 1) ANABOLISM
– 2) CATABOLISM

27. • Involves the synthesis
of complex molecules
from simpler molecules
which requires energy
input.
• Involves the breakdown
of complex molecules
into simpler molecules
involving hydrolysis or
oxidation and the
release of energy.

28. • Energy releasing processes, ones that
"generate" energy, are termed exergonic
reactions.
• Reactions that require energy to initiate the
reaction are known as endergonic reactions.
• All natural processes tend to proceed in such a
direction that the disorder or randomness of
the universe increases
Exergonic Reaction

30. • This kind of reaction is not termed a
spontaneous reaction. In order to go from
the initial state to the final state a
considerable amount of energy must be
imparted to the system.
• These kinds of reactions are associated with
a positive number (+G).
Endergonic Reaction

33. • The speed V means the number of reactions per
second that are catalyzed by an enzyme.
• With increasing substrate concentration [S], the
enzyme is asymptotically approaching its maximum
speed Vmax, but never actually reaching it.
• Because of that, no [S] for Vmax can be given.
• Instead, the characteristic value for the enzyme is
defined by the substrate concentration at its half-
maximum speed (Vmax/2).
• This KM value is also called Michaelis-Menten
constant.

34. Vo = Vmax
KM
• Vo = Initial reaction velocity
• Vmax = Maximum velocity
• Km = Michaelis constant
• [S] = Substrate concentration

35. Enzyme Nomenclature
Functional classification:
It is widely used. It takes into account the name of the
substrate of the enzyme and the type of catalyzed reaction. To
designate an enzyme is indicated:
the name of the first substrate
then the type of reaction catalyzed
Finally we add the suffix ase.
For example:
- Glucose-6-phosphate isomerase
- Isocitrate lyase
- Pyruvate carboxylase

36. When the enzyme uses two substrates and are described
by specifying both
radicals of the donor substrate
the acceptor substrate and then released the radical
exchanged the radical
the type of reaction
finally added ase
for example
- ATP-glucose phosphotransferase
- UDPglucose-fructose glucosyltransferase
- Glutamate pyruvate transaminase

37. Enzyme Nomenclature official
1: oxidoreductases, which catalyze electron transfer
2: The transferases, which catalyze the transfer of groups
3: hydrolases which catalyze hydrolysis reactions
4: lyases, which catalyze the addition of groups to double
bonds or vice versa
5: isomerases which catalyze the transfer of groups in one
molecule to produce isomeric forms (the conversion of an
amino acid D-amino acid in L 'for example)
6: ligases, which form links CC, CS, CN and CO during
condensation reactions coupled with the use of ATP.

38. The different types of enzymes:
• 4.1 - of redox enzymes and oxygen fixation
• 4.1.1 - dehydrogenation of the alcohol,
carbonyl or
• carboxyl
• 4.1.2 - dehydrogenases appear by double
bonds
• 4.1.3 - dehydrogenases acting on functions
nitrogenous
• 4.1.4 - enzymes involved in the transfer of
electrons in the mitochondria
• 4.1.5 - oxygenases
• 4.2 - transferases
• 4.2.1 - enzymes transferring a methyl group
• 4.2.2 - the transferring enzymes radicals has
more carbons
• 4.2.3 - the transferring enzymes of
carbohydrate molecules
• 4.2.4 - aminotransferases
• 4.2.5 - Phosphotransferases
• 4.3 - hydrolases
• 4.3.1 - carbohydrate hydrolases
• 4.3.2 - hydrolases phosphoric esters of
monosaccharides
4.3.3 lipid hydrolases
4.3.4 - hydrolases of peptides and proteins
4.3.5 - hydrolases nucleosides, nucleotides and
nucleic acids
4.3.6 - hydrolase esters or phosphoric anhydride
4.4 - lyases and synthases
4.4.1 - decarboxylases
4.4.2 - aldehyde-lyases
4.4.3 - acyl-lyase or acylsynthase
4.4.4 - hydratases and dehydratases
4.5 - isomerases
4.5.1 - epimerization
4.5.2 - intramolecular redox
4.5.3 - transport of radicals
4.6 - ligases (synthetases)
4.6.1 - forming links ligases c-o
4.6.2 - bond forming ligase c-c
4.6.3 - links ligases c-s
4.6.4 - links ligases c-n

39. • A non protein component of enzymes is called the
cofactor.
• If the cofactor is organic, then it is called a coenzyme.
• Coenzymes are relatively small molecules compared to
the protein part of the enzyme.
• Many of the coenzymes are derived from vitamins.
• The coenzymes make up a part of the active site, since
without the coenzyme, the enzyme will not function.
Enzyme Cofactor

40. • In the graphic on the left is the structure for the
coenzyme, NAD+, Nicotinamide Adenine
Dinucleotide.
• Nicotinamide is from the niacin vitamin.
• The NAD+ coenzyme is involved with many types
of oxidation reactions where alcohols are
converted to ketones or aldehydes.
Enzyme Cofactor

41. Vitamin Coenzyme Function
niacin
nicotinamide adenine
dinucleotide (NAD+)
oxidation or
hydrogen transfer
riboflavin
flavin adenine
dinucleotide (FAD)
oxidation or
hydrogen transfer
pantothenic
acid
coenzyme A (CoA) Acetyl group carrier
vitamin B-12 coenzyme B-12
Methyl group
transfer
thiamin (B-1)
thiaminpyrophosphate
(TPP)
Aldehyde group
transfer

42. • Coenzyme Q10 is a fat-soluble nutrient also known as
CoQ10, vitamin Q10, ubidecarenone, or ubiquinone.
• It is a natural product of the human body that is
primarily found in the mitochondria, which are the
cellular organelles that produce energy.
• It occurs in most tissues of the human body; however,
the highest concentrations are found in the heart, liver,
kidneys, and pancreas.
• Ubiquinone takes its name from a combination of the
word ubiquitous, meaning something that is found
everywhere, and quinone 10.
Co-enzymes

43. • Quinones are substances found in all plants
and animals.
• The variety found in humans has a 10-unit
side chain in its molecular structure.
• Apart from the important process that
provides energy, CoQ10 also stabilizes cell
membranes and acts as an antioxidant.
• In this capacity, it destroys free radicals, which
are unstable molecules that can damage
normal cells.

44. • Enzyme inhibitors are molecules that interact in
some way with the enzyme to prevent it from
working in the normal manner.
• There are a variety of types of inhibitors
including: nonspecific, irreversible, reversible -
competitive and noncompetitive.
• Poisons and drugs are examples of enzyme
inhibitors.
Enzyme inhibitors

46. • A nonspecific inhibition effects all enzymes in
the same way.
• Non-specific methods of inhibition include any
physical or chemical changes which ultimately
denatures the protein portion of the enzyme
and are therefore irreversible.
Non Specific Inhibitor

47. • Temperature: Usually, the reaction rate increases
with temperature, but with enzyme reactions, a
point is reached when the reaction rate
decreases with increasing temperature.
• At high temperatures the protein part of the
enzyme begins to denature, thus inhibiting the
reaction.
Example:

48. • A competitive inhibitor is any compound
which closely resembles the chemical
structure and molecular geometry of the
substrate.
• The inhibitor competes for the same active
site as the substrate molecule.
• The inhibitor may interact with the enzyme at
the active site, but no reaction takes place.
Competitive Inhibitor

49. • The inhibitor is "stuck" on the enzyme and prevents
any substrate molecules from reacting with the
enzyme.
• However, a competitive inhibition is usually
reversible if sufficient substrate molecules are
available to ultimately displace the inhibitor.
• Therefore, the amount of enzyme inhibition depends
upon the inhibitor concentration, substrate
concentration, and the relative affinities of the
inhibitor and substrate for the active site.
Competitive Inhibitor

52. • A noncompetitive inhibitor is a substance that forms
strong covalent bonds with an enzyme and
consequently may not be displaced by the addition
of excess substrate.
• Therefore, noncompetitive inhibition is irreversible.
• A noncompetitive inhibitor may be bonded at, near,
or remote from the active site. In any case, the basic
structure of the enzyme is modified to the degree
that it ceases to work.
Non-Competitive Inhibitor

53. Noncompetitive Inhibitor Action:

54. • If the inhibition is at a place remote from the
active site, this is called allosteric inhibition.
• Allosteric means "other site" or "other
structure".
• The interaction of an inhibitor at an allosteric
site changes the structure of the enzyme so
that the active site is also changed.
Non-Competitive Inhibitor

55. • There are approximately 3000 enzymes which
have been characterised.
• These are grouped into six main classes
according to the type of reaction catalysed.
• At present, only a limited number are used in
enzyme electrodes or for other analytical
purposes.

56. 1.Oxidoreductases
• These enzymes catalyse oxidation and
reduction reactions involving the transfer of
hydrogen atoms or electrons.
• The following are of particular importance in
the design of enzyme electrodes.
• This group can be further divided into 4 main
classes.

57. – catalyse hydrogen transfer from the substrate to
molecular oxygen producing hydrogen peroxide as
a by-product. An example of this is FAD
dependent glucose oxidase which catalyses the
following reaction:
– b-D-glucose + O2 = gluconolactone + H2O2
Oxidases

58. Dehydrogenases
– catalyse hydrogen transfer from the substrate to a
nicotinamide adenine dinucleotide cofactor
(NAD+). An example of this is lactate
dehydrogenase which catalyses the following
reaction:
– Lactate + NAD+ = Pyruvate + NADH + H+

59. Peroxidases
– catalyse oxidation of a substrate by hydrogen
peroxide.
– An example of this type of enzyme is horseradish
peroxidase which catalyses the oxidation of a number
of different reducing substances (dyes, amines,
hydroquinones etc.) and the concomitant reduction
of hydrogen peroxide.
– The reaction below illustrates the oxidation of neutral
ferrocene to ferricinium in the presence of hydrogen
peroxide:
– 2[Fe(Cp)2] + H2O2 + 2H+= 2[Fe(Cp)2]+ + 2 H2O

60. – catalyse substrate oxidation by molecular oxygen.
– The reduced product of the reaction in this case is
water and not hydrogen peroxide.
– An example of this is the oxidation of lactate to
acetate catalysed by lactate-2-monooxygenase.
– lactate + O2 = acetate + CO2 + H2O
Oxygenases

61. 2.Transferases
• These enzymes transfer C, N, P or S containing
groups (alkyl, acyl, aldehyde, amino,
phosphate or glucosyl) from one substrate to
another.
• Transaminases, transketolases, transaldolases
and transmethylases belong to this group.

62. 3.Hydrolases
• These enzymes catalyse cleavage reactions or
the reverse fragment condensations.
• According to the type of bond cleaved, a
distinction is made between peptidases,
esterases, lipases, glycosidases, phosphatases
and so on.
• Examples of this class of enzyme include;
cholesterol esterase, alkaline phosphatase and
glucoamylase.

63. 4.Lyases
• These enzymes non-hydrolytically remove
groups from their substrates with the
concomitant formation of double bonds or
alternatively add new groups across double
bonds.

64. 5.Isomerases
• These enzymes catalyse intramolecular
rearrangements and are subdivided into;
» racemases
» epimerases
» mutases
» cis-trans-isomerases
• An example of this class of enzyme is glucose
isomerase which catalyses the isomerisation
of glucose to fructose.

65. 6.Ligases
• Ligases split C-C, C-O, C-N, C-S and C-halogen bonds
without hydrolysis or oxidation.
• The reaction is usually accompanied by the
consumption of a high energy compound such as ATP
and other nucleoside triphosphates.
• An example of this type of enzyme is pyruvate
carboxylase which catalyses the following reaction:
• pyruvate + HCO3- + ATP = Oxaloacetate + ADP + Pi

66. The End