Proteins and enzymes

1. South Kazakhstan
medical academy
Biological and biochemistry
Department.
Submitted to: Mam Kanzhigitova
Moldir Zharkynbekkyz.
Submitted by: Sohail Riaz.
Topic: Protein biochemistry.

2. Contents
Protein, metabolism,Support,
transport.
Defense, regulation, Motion.
Amino acids.
Amino acids classification.
Protein structure.
Denaturation of protein.

3. Contents
 Enzyme
 Active site
 Factors affecting enzyme activity
 Temperature,pH, substrate
concentration
 Enzyme inhibitors
 Types of enzyme inhibitors
 Reversible inhibitors
 Irreversible inhibitors

4. Proteins
2006-2007
Multipurpose
molecules

5. Proteins
 Most structurally & functionally diverse group of
biomolecules
 Function:
 involved in almost everything
 Metabolism
 Support
 Transport
 Regulation
 Motion

6. Metabolism
 Enzymes
 Biological catalysts – speed up chemical reactions
 Digestive enzymes aid in hydrolysis
o Lipase
o Amylase
o Lactase
o Protease
 Molecular Biology
o Polymerase
o Ligase
 Industry
o Dairy, baby food, rubber, beer, photography, contact
lense cleaner

7. Support
 Structural proteins
 Keratin – hair and nails
 Collagen – supports ligaments, tendons, and skin
 Silk – cocoons and spider webs

8. Transport
 Channel and carrier proteins in the cell
membrane
 Allows substances to enter and exit the cell
 Transport molecules in blood
 Hemoglobin – transports oxygen in the blood

9. Defense
 Antibodies
 Combat bacteria and viruses

10. Regulation
 Hormones
 Intercellular messengers that influence metabolism
 Insulin – regulates the amount of glucose in the
blood and in cells
 Human growth hormone – its presence determines
the height of an individual
 Receptor Proteins
 Built into the membranes of nerve cells
 Detect chemical signals (neurotransmitters)
released by other nerve cells

11. Motion
 Muscle contraction
 Actin and myosin – make up muscle fibers
 Motor proteins within the cell
 Allow cell components to move from place to place
 Flagella- move the cell
 Cilia- move contents around the cell

12. Proteins
 Structure:
 monomer = amino acids
 20 different amino acids
 12 made by body
 8 essential amino acids (must get from food)
 polymer = polypeptide
 protein can be one or more polypeptide chains
folded & bonded together
 large & complex molecules
 complex 3-D shape
Rubisco
hemoglobin
growth
hormones

13. Amino acids
 Structure:
 central carbon (α carbon)
 amino group
 carboxyl group (acid)
 R group (side chain)
 variable group
 confers unique
chemical properties
of the amino acid —N—
H
H
C—OH
||
O
R
|
—C—
|
H

14. Nonpolar amino acids
 nonpolar & hydrophobic

15. Polar amino acids
 polar or charged & hydrophilic

16. Sulfur containing amino acids
 Form disulfide bridges
 cross links betweens sulfurs in amino acids
You wondered
why perms
smelled like
rotten eggs?
H-S – S-H

17. Building proteins
 Peptide bonds
 linking NH2 of one amino acid to
COOH of another
 C–N bond
 N terminus – C terminus
peptide
bond
dehydration synthesis

18. Protein structure & function
 Function depends on structure
 3-D structure
 twisted, folded, coiled into unique shape
hemoglobin
collagen
pepsin

19. Primary (1°) structure
 Order of amino acids in chain
 amino acid sequence determined by
gene (DNA)
 slight change in amino acid sequence
can affect protein’s structure & it’s
function
 even just one amino acid change can
make all the difference!
lysozyme: enzyme
in tears & mucus
that kills bacteria

20. Sickle cell anemia

21. Secondary (2°) structure
 “Local folding”
 folding along short
sections of polypeptide
 interaction between
adjacent amino acids
 H bonds between
backbones (O:H)
 -helix
 -pleated sheet
 Fibrous proteins – only
have secondary structure
 Keratin
 Silk

22. Secondary (2°) structure

23. Tertiary (3°) structure
 “Whole molecule folding”
 created when the secondary
structure fold and form bonds to
stabilize the structure into a
unique shape
 determined by interactions
between R groups
 Hydrophobic interactions
 anchored by
disulfide bridges
 Ionic Bonds between R groups
 Hydrogen bonds between backbones
 Van der Waals Force (velcro)
 Globular (spherical) proteins – have
tertiary structure
 enzymes

24. Quaternary (4°) structure
 two or more tertiary folded peptide subunits
bonded together to make a functional protein
 Hemoglobin – 4 polypeptides
 Collagen – 3 polypeptides
hemoglobin
collagen =
skin & tendons

25. Protein structure (review)
1°
2°
3°
4°
aa sequence
peptide bonds
H bonds
R groups
hydrophobic interactions,
disulfide bridges, ionic bonds
determined
by DNA
multiple
polypeptides
hydrophobic
interactions

26. Denature a protein
 Unfolding a protein/changes the shape
 disrupt 3° structure
 pH  temperature
 unravels or denatures protein
 disrupts H bonds, ionic bonds &
disulfide bridges
 destroys functionality

27. What is an enzyme?
globular protein
which functions as
a biological
catalyst, speeding
up reaction rate by
lowering activation
energy without
being affected by
the reaction it
catalyse
Active
site

28. Enzymes are protein in nature (?)
 Globular protein.
 Ribozymes are RNA molecule with
enzymatic activity.
 Catalytic behaviour of any enzyme
depends upon its primary, secondary,
tertiary or quaternary structure.
 Enzymes of digestive tract and those
found in blood are present in inactive form
called zymogen or proezymes.

29. Active site
 Enzymes are composed of
long chains of amino acids
that have folded into a very
specific three-dimensional
shape which contains an
active site.
 An active site is a region on
the surface of an enzyme to
which substrates will bind
and catalyses a chemical
reaction.

30. Enzymes are highly specific for the
type of the reaction they catalyze
and for their substrate.

33. Mechanism of enzyme action
The enzymatic reactions takes place by binding of
the substrate with the active site of the enzyme
molecule by several weak bonds.
E + S ‹--------› ES --------› E + P
Formation of ES complex is the first step in the
enzyme catalyzed reaction then ES complex is
subsequently converted to product and free
enzyme.

34. "Lock and key" or Template
model

35. Induced-fit model

36. e.g. H2O2
e.g. O2 + H2O
Progress of Reaction

37. Factors affecting reaction
velocity
Temperature
Hydrogen ion concentration (pH)
Substrate concentration
Enzyme concentration
Products of the reaction
Presence of activator/inhibitor
Allosteric effects
Time

38. Effect of Temperature
Temperature(
o
C)
Reaction
Velocity (v0)

39. Effect of pH
Reaction
Velocity (v0)
pH
Pepsin
Trypsin
q r

40. Rate of the reaction or velocity is directly
propostional to the Enzyme Concentration
when sufficient substrate is present.
Accumulation of Product in a reaction causes
inhibition of enzyme activity.

41. Effect of Substrate
Concentration
Substrate Concentration/arbitrary Units
Reaction
Velocity (v0)

42. Enzyme Inhibiton
Any substance that can diminish the velocity
of an enzyme catalyzed
These include drugs, antibiotics, poisons,
and anti-metabolites.
Useful in understanding the sequence of
enzyme catalyzed reactions, metabolic
regulation, studying the mechanism of cell
toxicity produced by toxicants.
Forms the basis of drug designing.

43. Types of Enzyme Inhibiton
 Reversible inhibitors
 Irreversible inhibitors

44. Reversible inhibitors can be
classified into :
 Competitive
 Non-competitive
 Un-competitive

45. Competitive Inhibition

46. Non-Competitive Inhibition

47. Un-competitive Inhibiton
Binds only to the enzyme-substrate
complex.
Does not have the capacity to bind to the
free enzyme.
Not overcome by increasing substrate
concentration.
Both the Km and Vmax are reduced.

48. Un-competitive Inhibiton
Enzyme
ES Complex
+ Inhibitor
ESI complex

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