L12 – Enzyme Regulation
Explain with examples the terms reversible inhibition and irreversible inhibition
Slide 62 – Enzyme inhibitors
• Competitive inhibitors block the enzyme active site
- Something that looks similar to the substrate as it goes to the same place as the
substrate
- Eg. Malonate inhibition of succinate dehydrogenase
• Non-competitive (reversible or irreversible) interfere in some other way with the catalytic
mechanism
- Reversible inhibition of a Mg2+-requiring enzyme by addition of chealator (EDTA)
- Irreversible organophosphorus inhibition of cholinesterase
- Inhibitor is non-competitive,
binds to a different location and doesn’t directly compete with the substrate
- Binding of inhibitor affects catalysis when complex is formed
Explain the different effects of competitive, non-competitive inhibitors on enzyme kinetic
parameters
Slide 66 – Competitive inhibitors alter the apparent Km, not the Vmax
, • Km is different in presence of inhibitor
• Vmax is same in the presence of inhibitor
- Whatever concentration of inhibitor, always possible to outcompete inhibitor with infinite
substrate concentration, changing Km as they compete for the same place, but Vmax
remains
• Second red line: absence of inhibitor
- As Km becomes bigger, 1/Km becomes smaller
Slide 67 – Effect of a non-competitive inhibitor enzyme activity
• Km is the same, Vmax is different
Indicate with named examples, two clinical uses of enzymes inhibitors
Slide 69-70 – Control of angiotensin production
Explain with examples the terms reversible inhibition and irreversible inhibition
Slide 62 – Enzyme inhibitors
• Competitive inhibitors block the enzyme active site
- Something that looks similar to the substrate as it goes to the same place as the
substrate
- Eg. Malonate inhibition of succinate dehydrogenase
• Non-competitive (reversible or irreversible) interfere in some other way with the catalytic
mechanism
- Reversible inhibition of a Mg2+-requiring enzyme by addition of chealator (EDTA)
- Irreversible organophosphorus inhibition of cholinesterase
- Inhibitor is non-competitive,
binds to a different location and doesn’t directly compete with the substrate
- Binding of inhibitor affects catalysis when complex is formed
Explain the different effects of competitive, non-competitive inhibitors on enzyme kinetic
parameters
Slide 66 – Competitive inhibitors alter the apparent Km, not the Vmax
, • Km is different in presence of inhibitor
• Vmax is same in the presence of inhibitor
- Whatever concentration of inhibitor, always possible to outcompete inhibitor with infinite
substrate concentration, changing Km as they compete for the same place, but Vmax
remains
• Second red line: absence of inhibitor
- As Km becomes bigger, 1/Km becomes smaller
Slide 67 – Effect of a non-competitive inhibitor enzyme activity
• Km is the same, Vmax is different
Indicate with named examples, two clinical uses of enzymes inhibitors
Slide 69-70 – Control of angiotensin production
