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Questions and Answers
What is enzyme inhibition?
What is enzyme inhibition?
Enzyme inhibition is a process that decreases or stops the activity of an enzyme.
What are the two main types of enzyme inhibition?
What are the two main types of enzyme inhibition?
Competitive inhibitors bind to the active site of the enzyme.
Competitive inhibitors bind to the active site of the enzyme.
True
Non-competitive inhibitors can be relieved by increasing substrate concentration.
Non-competitive inhibitors can be relieved by increasing substrate concentration.
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Which of the following is NOT a characteristic of competitive inhibition?
Which of the following is NOT a characteristic of competitive inhibition?
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Which of the following is a characteristic of non-competitive inhibition?
Which of the following is a characteristic of non-competitive inhibition?
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What is the drug allopurinol used for?
What is the drug allopurinol used for?
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How does dicumarol work?
How does dicumarol work?
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Match the following enzyme inhibitors with their mechanism of action:
Match the following enzyme inhibitors with their mechanism of action:
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Study Notes
Enzyme Inhibition
- Enzyme inhibition is a process that decreases or stops enzyme activity.
- Inhibitors are substances that reduce or abolish the rate of enzyme action.
- Inhibition types are categorized based on the similarity between the inhibitor and the substrate:
- Competitive Inhibition: Involves structural similarity between the inhibitor and the substrate. The inhibitor and substrate compete to bind to the enzyme's catalytic site. This inhibition is reversible. Increasing substrate concentration can reverse the inhibition. It doesn't affect the maximum reaction rate (Vmax), but increases the Michaelis constant (Km).
- Non-competitive Inhibition: The inhibitor lacks structural similarity with the substrate. It binds to a different site on the enzyme, changing its shape and hindering enzyme activity; this is an irreversible process. Increasing substrate concentration does not reverse the inhibition. This inhibition decreases the maximum reaction rate (Vmax), but does not change the Michaelis constant (Km).
Examples and Clinical Use
- Folic acid synthesis: Sulfonilamide inhibits dihydropteroate synthase (DHPS).
- Prothrombin synthesis: Dicumarol inhibits vitamin K epoxide reductase.
- Xanthine oxidase: Allopurinol inhibits xanthine oxidase, which is involved in the formation of uric acid.
- Alcohol dehydrogenase: Ethanol is an example of an inhibitor that converts to acetaldehyde.
Inhibition of Specific Groups
- Sulphahydryl (-SH) group: Many enzymes depend on free SH groups. Heavy metals like mercury (Hg++) and lead (Pb++) inhibit these groups.
- Cofactors: Cyanide hydrazine inhibits coenzyme pyridoxal phosphate (PLP).
- Metal ion activators: Oxalate chelates calcium ions, preventing blood clotting. Fluoride chelates magnesium ions, inhibiting glycolysis.
Case Studies
- Gout: Allopurinol inhibits xanthine oxidase which is involved in the formation of uric acid (urate).
- Ischemic heart disease: Dicumarol inhibits a coagulation enzyme to thin the blood.
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Description
Explore the critical concepts of enzyme inhibition, including competitive and non-competitive inhibition. Understand how inhibitors affect enzyme activity and the implications on reaction rates. This quiz will test your knowledge of enzymatic processes and their classifications.
