basics of enzymes

1. ENZYMES
Nature, Classification and
Mechanism of action
By: Kuljit kaur
Lecturer
Kanya Maha Vidyalaya
Kuljitk03@gmail.com

2. Do watch these videos before you
continue
https://www.youtube.com/watch?v=XTUm-75-
PL4 (This one is a fun video)
https://www.youtube.com/watch?v=ozdO1mLX
BQE

3. INTRODUCTION
They are the BIO-CATALYST.
• Biological in origin and regulate specific function.
• Water soluble
• Colloidal organic macromolecules.
• Wholly or partially proteinaceous.
• Produced in microamounts.
• Trigger rate of metabolism..
• Not itself changed .
• Regenerated .
• Does not change equilibrium constant .
• Increases rate of reaction.

4. • Specific – substrate and condition specific.
• Enzymes :1. endoenymes (metabolic enzymes)
2. exoenzymes (digestive enzymes)

6. Discovery of enzymes
• First reported by W. Kuhne but Edward
buchner first isolated it from the yeast cells.
• Buchner gave term enzyme : en- in, zyme-yeast
• So enzymes means “inside the yeast”.

7. IMPORTANCE OF ENZYMES
• Metabolic pathway is stepped process and
each step is catalysed by enzymes.
• A biological reaction needs enzyme for two
reasons: 1. metabolic actions occur at
controlled temperature.
2. Act as biocatalyst.
Absence of enzymes may be fatal.

8. CHEMICAL NATURE
• Wholly or partially
proteinaeous .
• Specific 3-
dimesnional tertiary
structure.
• All proteins are not
enzymes.

9. • The proteinous nature of enzymes is evident from:
1.
2.
3.Enzymes like proteins are macromolecules.
4.Enymes and proteins both do not pass through
dialyzing membrane.
5.Both are colloidal in nature.
Proteins and
enzymes boiled coagulation
enzymes hydrolysis Amino acids

10. Classification on basis of chemistry
Components of
compound
enzyme:
ENZYMES
Pure proteinous
enzymes
Conjugated or
compound
proteinous
enymes
A) Apoenzymes B) Co-factor

11. Concept of Apoenzyme and
Holoenzyme
• HOLOENZYME: It is always a conjugated
protein.
• Apoenzyme: protein part
• Cofactor/prosthetic group : non-protein part.
APOENZYME
COFACTOR
Or
Prosthetic
group
HOLOENZYME

12. • Before joining cofactor, apoenzyme is inactive
and is also called ZYMOGEN or
PROENZYME.
• Cofactors are not covalently bound but are
tightly bound.
• Organic prosthetic groups can be covalently
bound.

13. CATALYST AND ENZYME
• Catalyst increases the rate of chemical reactions while
enzymes ehances the rate of biochemical reactions.
• So the enzymes are BIO-CATALYST.
• Similarities :1. Both are effective in very small
amount.
2.Both remain unchanged in reaction qualitatively and
quantitatively.
3.Have no effect on equilibria; they just speed up the
reaction.
4. They lower the value of activation energy.

14. Classification of enzymes

15. S.No. Class Major subclasses
1. Oxidoreductases Dehydrogenases,
Oxidases,Reductases,Oxygenases
2. Transferases Transaldolases, Phosphotransferases,Kinases
3. Hydrolases Peptidases,Deaminases
4. Lyases Decarboxylases,Aldolases
5. Isomerases Mutases, isomerases, Racemases
6. Ligases Synthetases , Carboxylases
https://www.youtube.com/watch?v=0
Nr9Pc00qOk

16. Mechanism of enzyme action
• https://www.youtube.com/watch?v=hXeMb-
CBTW0
Lock and key mechanism
• https://www.youtube.com/watch?v=V8TOWTp71tE
Induced fit mechanism

18. Nature of active sites in lock and key
mechanism
• Active sites contain special groups e.g. –OH
group ,-NH2,-COOH,-SH

20. Induced fit mechanism

21. Michaelis-Menten Hypothesis
• The minimum amount
of energy required to
bring the substrate
molecules of one mole
in the reactive form, is
called activation
energy.
• https://www.youtube.c
om/watch?v=np2JUCVv
BwQ

22. Factors affecting enzyme activity
• Substrate concentration
• Temperature
• pH
• Enzyme concentration
https://www.youtube.com/watch?v=ojXUxR0gk
AI

23. Substrate concentration
• First stated in 1913, it assumes the
rapid reversible formation of a
complex between an enzyme and
its substrate (the substance upon
which it acts to form a product). It
also assumes that the rate of
formation of the product, P, is
proportional to the concentration
of the complex. The velocity of
such a reaction is greatest when
all the sites at which catalytic
activity can take place on the
enzyme molecules (active sites)
are filled with substrate—i.e.,
when the substrate concentration
is very high.

24. Temperature
• Temperature plays an important role in
biology as a way to regulate reactions.
Enzyme activity increases as
temperature increases, and in turn
increases the rate of the reaction. This
also means activity decreases at colder
temperatures. All enzymes have a range
of temperatures when they are active,
but there are certain temperatures
where they work optimally.
• While higher temperatures do increase
the activity of enzymes and the rate of
reactions, enzymes are still proteins,
and as with all proteins, temperatures
above 104 degrees Fahrenheit, 40
degrees Celsius, will start to break
them down.

25. pH

26. Enzyme concentration
• In the presence of high substrate concentration,
increase in enzyme concentration accelerates
the velocity of enzyme-catalysed reactions.
• V∝[E]
V=K[E]
Where is V is velocity of reaction, [E]is enzyme
concentration and k is constant.