Inhibitors:
- stop enzymes working
- decrease rate of reaction
- block active sites
An inhibitor is any substance that slows down the rate of an enzyme controlled reaction by affecting the enzyme molecule.
Competitive Inhibitors
- Similar shape to substrate
- Occupy active sites
- Form enzyme-substrate inhibitor complexes
- Enzyme-substrate complex decreases rate of reaction
- Level of inhibition depends on concentration of substrate/inhibitor
- most don’t bind permanently, making the reaction reversible
Alcohol Dehydrogenase and ethylene glycol
- An ethylene glycol overdose can be fatal
- In the liver, it is broken down into oxalic acid (very toxic) by alcohol dehydrogenase
- By administering a large dose of ethanol, you can prevent oxalic acid production by filling all active sites with a competitive substance.
Non-competitive Inhibitors
- Bind elsewhere on the enzymes
- Alosteric site
- Affects the tertiary structure leading to a change in the shape of the active site
- Level of inhibition depends on concentration of inhibitor
- Many bind permanently, making the reaction irreversible
Protein Pump Inhibitors (PPIs)
- Stomach acidity is determined by H⁺ ion concentration
- Inhibiting the pumps reduces H⁺ ion production
- Which increases the pH of stomach acid
- Leading to lower acidity
- A PPI binds to an alosteric site and changes the tertiary shape of the enzyme, preventing the complementary substrate from binding
End production inhibition
- Product of one reaction is an inhibitor to the enzyme that produced it.
Biochemical reactions
- Products of one reaction becomes substrate for the next
- One product may inhibt the enzyme that produced it, limiting the rate of reaction and creating a negative feedback loop