Công nghệ ezyme

1. ENZYME
 Characteristic
 Mechanism
 Factors

2. Definition
 Enzymes are protein produced by the
cells of living organism act as
biological catalyst by controlling and
accelerating the rate of biochemical
reactions in the cell at fairly low
temperatures.
 Without enzymes, biochemical reactions
become too slow to maintain the life supporting
process in an organism.

3. EA
with
enzyme
Figure 5.5B
Reactants
Products
EA
without
enzyme
Net
change
in energy

4. Important Terms…
 The activation energy, EA
 Is the initial amount of energy needed to
start a chemical reaction
 Is often supplied in the form of heat from
the surroundings in a system

5. Cont…
 The active site
 Is the region on the enzyme where the
substrate binds
Figure 8.16
Substate
Active site
Enzyme
(a)

6. Cont…
 Cofactors
 Are nonprotein enzyme helpers
 Coenzymes
 Are organic cofactors

7. Enzyme Inhibitors
 Competitive inhibitors
 Bind to the active site of an enzyme, competing
with the substrate
(b) Competitive inhibition
A competitive
inhibitor mimics the
substrate, competing
for the active site.
Competitive
inhibitor
A substrate can
bind normally to the
active site of an
enzyme.
Substrate
Active site
Enzyme
(a) Normal binding

8. Cont…
 Noncompetitive inhibitors
 Bind to another part of an enzyme,
changing the function
A noncompetitive
inhibitor binds to the
enzyme away from
the active site, altering
the conformation of
the enzyme so that its
active site no longer
functions.
Noncompetitive inhibitor
(c) Noncompetitive inhibition

9. Competitive and noncompetitive inhibition

10. Types of enzymes
1. Intracellular enzyme
 Enzymes that are produces in certain cells
and remain to react in the cell
 These enzymes could exist either in
cytoplasm (in organelles) or nucleus.
1. Extracellular enzyme
 Some enzymes are produced by cell but then
transported out of the cell for action outside
the cell

11. Enzyme
(sucrase)
Active
site
1
2
3
Substrate
(sucrose)
Enzyme available
with empty active
site
Substrate
binds to
enzyme with
induced fit
Substrate is
converted to
products
4
Products are
released
Glucose Fructose
 How an
enzyme
works
 The enzyme
is unchanged and can repeat the process
Figure 5.6

12. CharaCTerisTiCs
1. Enzymes generally act quickly
 the speed of reaction is usually stated in ‘turnover
number’ (refer to the number of substrates)
1. Enzymes are not damaged
 however, this does not mean that enzymes can be
used repeatedly forever without replacement
1. Enzymes can react in both direction
2. Enzymes are specific
 each enzymes limited to one specific reaction that
involved one specific substrate only

13. Cont…
5. An enzymes molecule is usually bigger
than its substrates
6. All enzymes are proteins and not all
protein are enzymes
7. Enzymes are complex globular protein
and three dimensional.
Main function of enzymes
 Increase the rate of chemical reaction by
lowering activation energy

14. MechanisMs of enzyMes
There are 2 main hypothesis explaining
the mechanism of enzyme action :
 The lock-and-key hypothesis
 The induced-fit hypothesis
Simple mechanism

15. Lock-and-key
hypothesis
 The hypothesis proposed that the active site and substrate are exactly
complementary
 An enzyme is a large globular protein with specific three dimensional
shape.
 It has a site called the active site.
 In the lock-and-key hypothesis, the shape of the substrate (‘key’) fits
into the active site of the enzyme (‘lock’) forming and enzyme-
substrate complex
 Reaction takes place and products are formed and released

16. Induced-fit hypothesis
 It is a modified version of the lock-and-key
hypothesis
 The hypothesis suggested that active site is
flexible and is not exactly complementary to the
shape of the substrate
 An enzyme collides with the substrate molecule.
The substrate binds to the active site
 The binding induces a slight change in the
shape of the enzyme to enclose the substrate
making the fit more precise.

17. factors
 Any factors that affect the activity of an
enzyme will change the rate of the
reaction catalysed by that enzyme
 Enzyme characteristic are affected by
several factors such as temperature,
pH, substrate and enzyme
concentration.

18. The effect of Temperature
 At lower temperature, enzymes
are not active
 As the temperature rises, the
substrate and the enzyme
molecules move rapidly and are
more likely to collide
 The increase in temperature to
a specific level can increase the
rate of the enzyme activity until
the optimum temperature rate.
 After the optimum temperature
the enzymes activities
decreased and totally stopped at
temperature of ±60o
C

19. The effect of pH
 All enzymes have a specific
optimum pH at which they
function most efficiently
 Most enzyme act at a pH in
range of 5 – 9, and reactions
most efficiently at a pH of 7
 The small change in pH can
produce a large effect on enzyme
activity
 A pH that is extreme usually
destroy enzymes

20. Cont…
 However, there are exceptions for certain
enzymes such as:
 Pepsin pH 1.5 – 2.5 (acidic)
 Rennin pH 8.5 (alkaline)

21. The effect of Enzyme
Concentration
 The rate of an enzyme-catalysed reaction is
directly proportional to the concentration
of the enzymes if substrates are present in
excess concentration and no other factors
are limiting

22. The effect of Substrate
Concentration
 Increasing the substrate concentration can give a
increasing in reaction rate
 At lower concentrations the rate increase in direct
proportion to the substrate concentration
 At higher substance
concentration the rate of
reaction becomes
constant

23. classification
 Enzymes can be classified by the kind of
chemical reaction catalyzed:
1. Hydrolases
2. Lyases
3. Isomerase
4. Ligases
5. Transferases
6. Oxidoreductase
 This classification system introduced in 1961
by IUB (International Union of Biochemistry)