Effect of temperature and PH on enzyme activity

1. Effect of temperature and PH on enzyme activity
Course code: 421204420
Student name: Shaden Mohammed Motaab Almohammed
Semester :2nd
Academic Year: 1441/1442
Student number :

2. FACTORS AFFECTING ENZYME
ACTION
• Effect of Temperature
• Effect of pH
• Effect of Enzyme Concentration
• Effect of Product Concentration
• Effect of Substrate Concentration
• Effect of Activators and Coenzymes
• Effect of Modulators and Inhibitors
• Effect of Time
Activity of
enzymes is
markedly
affected by
several factors
such as
temperature, pH,
conc. of other
substances,
presence of
activators or
inhibitors, etc.

3. Effect of Temperature
Each enzyme is most active at a specific temperature which is
called its optimum temperature. Temperature increases the
total energy of the chemical system with the result the
activation energy is increased. The exact ratio by which the
velocity changes of 10oC temperature rise is the Q10 or
temperature coefficient. Reactions velocity almost doubles
with 10oC rise (Q10 = 2) in many enzymes. Activity of enzyme
progressively decreases when the temperature of reaction is
below or above the optimum temperature. However, increase
in temperature also causes denaturation of enzyme.

4. Effect of Temperature
Note
The shape of the curve is bell-shape. Most of
the enzymes of human system have an
optimum temperature within the range of 35–
40oC. Thus, the optimum temperature is that
temperature at which the activity of the
enzyme is maximum.

5. Effect of Temperature

6. Effect of pH
. The rate of enzymatic reaction also depends on pH of the
medium. The enzymatic activity is maximum at a particular
pH which is called its optimum pH. The optimum pH of most
enzymes .

7. Effect of pH
• Hydrogen ions in the medium may alter the ionisation
of active site or substrates. Ionisation is a requirement
for ES complex formation and
• pH may influence the separation of coenzyme from
holoenzyme complex. At a very low or high pH the
H-bonds may be inactivated in the protein structure,
destroying its 3D structure. The optimum pH may
vary from substrate to substrate for an enzyme acting
on a number of substrates because of the ES complex
formation and ionisation will vary from substrate to
substrate.

8. Effect of pH

9. Distinguishing between effect of PH
and temperature on enzymes

10. References
1. MN Chatterjea - Textbook of Medical
Biochemistry, 8th Edition
2. Jypee Textbook of BIOCHEMISTRY for
Medical Students (Seventh Edition)