Enzyme Inhibitors- Metabolic Pathways and Examples of Inhibitors

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  • Created by: Freja
  • Created on: 24-04-21 10:51
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  • Enzyme Inhibitors
    • Drugs and Metabolic Poisons
      • Medicinal Drugs
        • Some antibiotics e.g. penicillin inhibits the enzyme transpeptid-ase, which catalyses the formation of proteins in the bacterial cell walls. This weakens the cell wall and prevents the bacterium from regulating its osmotic pressure. As a result the cell bursts and the bacterium is killed.
        • Antiviral Drugs- e.g. reverse transcriptase inhibitors inhibit the enzyme reverse transcriptase, which catalyses the replication of viral DNA, which prevents the virus from replicating
      • Metabolic Poisons interfere with metabolic reactions.
        • Malonate inhibits succinate dehydrogen-ase, which also catalyses respiration reactions.
        • Arsenic inhibits the action of pyruvate dehydrogen-ase, another enzyme that catalyses respiration reactions.
        • Cyanide is an irreversible inhibitor of cytochrome c oxidase, an enzyme which catalyses respiration reactions. Cells that cannot respire die.
    • Metabolic Pathways and End-Product Inhibition
      • A metabolic pathway is a series of connected metabolic reactions, where the product of the first reaction takes part in the second reaction. Each reaction is catalysed by a different enzyme.
      • Product and end-product inhibition are reversible. So when the level of product drops, the level of inhibition starts to fall and the enzyme can start to function again, so more product is made.
      • Many enzymes are inhibited by the product of the reaction they catalyse, this is known as product inhibition.
      • End-product inhibition regulates the pathway and controls the amount of end-product that gets made.
      • End-product inhibition is when the final product in a metabolic pathway inhibits an enzyme that acts earlier on the pathway
    • Enzyme Inhibitors Can Protect Cells
      • Enzymes are sometimes synthesised as inactive precursors in metabolic pathways to prevent them from causing damage.
      • Part of the precursor molecule inhibits its action as an enzyme. Once this part is removed (e.g. through a chemical reaction) the enzyme becomes active
      • For example, some proteases, which break down proteins, are synthesised as inactive precursors to stop them damaging proteins in the cell in which they are made.

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