1. ENZYME ACTIVITY
11a Bilegdemberel

2. ACTIVE SITE
• Enzymes are globular proteins. In one part of the molecule, there is an area called the
active site, where the substrate molecule can bind. This produces an enzyme-substrate
complex. The 3D shape of the active site fits the substrate perfectly, so only one type of
substrate can bind with the enzyme. The enzyme is specific for that substrate

3. ENZYMES
• An enzyme is a protein that acts as a biological catalyst--- that is, it speeds up a
metabolic reaction without itself being permanently changed.
• The substrate present at the start of an enzyme-catalysed reaction is called the substrare.
The product is the new substance or substances formed.
• Virtually every metabolic reaction which takes place within a living organism is catalysed
by an enzyme. Many enzyme names end in –ase, for example amylase.
• Enzymes are globular proteins. Like all globular proteins, enzyme molecules are coiled
into a precise three-dimensional shape, with hydrophillic r groups (side chains) on the
outside of the molecule ensuring that they are soluble.

4. ACTIVATION ENERGY
• Substrates generally need to be supplied with energy to cause them to change into
products. The energy required to do this is called activation energy.
• Enzymes are able to make substances react even at low temperatures. They reduce the
activation energy needed to make the reaction takes place. They do this by distorting the
shape of the substrate molecule when binds at the enzyme’s active site

5. EFFECT OF PH
Enzyme pH Optimum
• Enzymes are affected by changes in pH. The most favorable pH value - the point where
Lipase (pancreas)
the enzyme is most active - is known as the optimum pH.
8.0
Lipase (stomach) 4.0 - 5.0
• Extremely high or low pH values generally result in complete loss of activity for most
enzymes. pH (castor a factor in the stability of enzymes. As with activity, for each enzyme
Lipase is also oil) 4.7
there is also a region of pH optimal stability.
Pepsin 1.5 - 1.6
Trypsin 7.8 - 8.7
Urease 7.0
Invertase 4.5
Maltase 6.1 - 6.8
Amylase (pancreas) 6.7 - 7.0
Amylase (malt) 4.6 - 5.2
Catalase 7.0

6. TEMPERATURE
• Like most chemical reactions, the rate of an enzyme catalysed reaction increases as the
temperature is raised
• Above a certain temperature, however, hydrogen bonds holding the enzyme molecule in
shape begin to break. This causes the tertiary structure of the enzyme to change, an
effect called denaturatio. This affects the shape of its active site. It becomes less likely
that the substrate molecule will be able to bind with the enzyme, and the rate of reaction
slows down

7. ENZYME CONCENTRATION
• The greater the concentration of enzyme, the more frequent the collisions between
enzyme and substrate, and therefore the faster the rate of the reaction. However, at very
high enzyme concentrations, the concentration of substrate may become a limiting factor,
so the rate does not continue to increase if the enzyme concentration is increased

8. SUBSTRATE CONCENTRATION
• The greater the concentration of substrate, the more frequent the collisions between
enzyme and substrate, and therefore the faster the rate of the reaction. However, at high
substrate concentration, the concentration of enzyme may become a limiting factor, so the
rate does not continue to increase if the substrate concentration is increased..

9. COENZYMES
• A nonproteinaceous organic substance that usually contains a vitamin or mineral and
combines with a specific protein, the apoenzyme, to form an active enzyme system.

10. • Not all enzymes have optimum temperatures of 40 degree Celcius. Bacteria and algae
living in hot springs such as this one in Yellowstone National Park, USA, are able to
tolerate very high temperatures. Enzymes from such organisms are proving useful in
various industrial applications.

11. INHIBITORS
• An inhibitor is a substance that slows down the rate at which an enzyme works.

12. INHIBITORS
Inhibitor binds to active Inhibitor binds elsewhere
site on enzyme on enzyme
Inhibitor binds briefly Competitive reversible Non-competitive reversible
Inhibitor binds permanently Non-competitive Irreversible Non-competitive irreversible

13. CONCLUSION
• Enzymes are globular proteins, which act as catalysts by lowering activation energy.
• Each enzyme acts on only one specific substrate, because there has to be a perfect
match between the shape of the substrate and the shape of the enzyme’s active site to
from an enzyme-substrate complex.
• Anything which affects the shape of the active site, such as high temperature, a change in
pH or the binding of a non-competitive inhibitor with the enzyme, will slow down the rate
of the reaction.
• Competitive inhibitors also slow down the rate of reaction, by competing with the
substrate for the active site of the enzyme.

14. THANK YOU FOR YOUR ATTENTION