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BIOCHEMISTRY
FACTORS THAT AFFECT ENZYME ACTIVITY
The effect of enzyme inhibition
Irreversible inhibitors:
These
combine with the functional groups of the amino acids
in the active site, irreversibly.
Examples:
nerve gases and pesticides, containing organophosphorus,
combine with serine residues in the enzyme
acetylcholine esterase.
Reversible inhibitors:
These can be washed out of the solution of enzyme by
dialysis. There are two categories.
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Competitive:
These compete with the substrate molecules for
the active site.
The
inhibitors action is proportional to its
concentration. |
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Usually this type of inhibitor resembles the
substrate’s structure closely |
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If
more substrate is added, the effect of the
inhibitor is reduced.
Non-competitive:
These are not influenced by the concentration of
the substrate. It inhibits by binding
irreversibly to the enzyme but
not at the active site
Examples
Cyanide combines with the Iron in the enzymes
cytochrome oxidase.
Heavy metals, Ag or Hg, combine
with –SH groups.
These can be removed by using a chelating agent
such as EDTA. |
Applications of inhibitors
Negative feedback See end point or end product
inhibition
Poisons snake bite, plant alkaloids and nerve gases.
Medicine antibiotics, sulphonamides, sedatives and
stimulants
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© Paul Billiet 2009 |
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