Enzyme Kinetics - Irreversible Inhibitors

Irreversible Inhibitors

Finally there is one more group of compounds which are sometimes considered to be inhibitors. These form covalent bonds with the enzyme and are therefore essentially irreversible. Such compounds are probably best considered to be inactivators rather than inhibitors. They are most useful as chemical modifying regents. Iodoacetic acid and diisopropyl phosphofluoridate are examples of irreversible inhibitors.

Irreversible inhibition occurs only rarely in vivo, but there are a few important cases of which you should be aware. Usually these are cases of poisoning. Cyanide is found in the seeds of some fruits and can react with the metal ions found in some enzymes . The compound physostigmine is found in calabar beans and is a nerve toxin because it inhibits acetylcholinesterase.

Monoamine oxidase (MAO) is an enzyme which is believed to be involved in depression. It acts to oxidize certain biogenic amines including norepinephrine and serotonin.

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