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Transcript of Enzyme inhibitors
While the inhibitor is attached to the enzyme, the enzyme's function is blocked.
This is reversible because if the inhibitor leaves the enzyme, its
shape is restored
and the enzyme can now accept substrate.
Comparing Enzyme affinities
Measuring how well an enzyme performs by finding the theoretical maximum rate (V-max) of the reaction it catalyzes is, a key step to allowing the comparability of affinities.
At V-max ,
all the enzyme molecules are bound to substrate molecules.
Some more V-max
Example of competitive inhibition
This is when a substance reduces the rate of activity of an an enzyme by
binding to areas of the enzyme molecule other than the active site
While the inhibitor is bound to the enzyme, it seriously disrupts the normal arrangement of
hydrogen bonds and hydrophobic interactions
holding the enzyme in its 3-D shape.
Competitive, reversible inhibition
The active site of an enzyme fits one particular substrate. However, it is possible for some other molecule to bind to an enzyme's active site if it is very similar in shape to the enzyme's substrate.
The molecule will be called an
Enzyme inhibitors Among Other things
While the inhibitor is bound to the active site, it prevents a substrate molecule from occupying that site. So,
inhibitors reduce the rate of the reaction
The resulting distortion ripples across the molecule to the active site, making the enzyme
unsuitable for the substrate
How V-max is measured; The reaction rate is measured at different substrate concentrations while keeping the enzyme concentration constant. As substrate concentration is increased, reaction rate rises until the reaction reaches its maximum rate.
Due to this inhibition being reversible, the
same quantity of product is formed
This is because the substrate continues to
use any enzyme that is unaffected by the inhibitor
NOTE: The enzyme is not denatured when the inhibitor leaves, hence the reversibility of the process.
Km is the substrate concentration at which an enzyme works at
half its maximum rate
(1/2V-max). At km, half the active sites are occupied by substrate.
the higher the affinity of the enzyme for the substrate, the lower the substrate concentration needed for 1/2 V-max to be reached.
Thus, the Michaelis-Menten (Km) constant is a measure of the affinity of the enzyme for its substrate.
Enzymes can be immobilized- for example, by trapping them in jelly (alginate) beads. This is commercially used because the
enzyme can be re-used
product is separate from (uncontaminated by) the enzyme