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Enzyme Inhibitors Explained

Feb 10, 2025

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Medicosis Perfectionalis: Understanding Enzyme Inhibitors

Introduction

  • Discusses enzyme inhibitors: competitive, non-competitive, mixed, and uncompetitive.
  • Enzymes as catalysts: increase reaction speed, lower activation energy without changing.
  • Two main sites on enzymes:
    • Active Site: where competitive inhibitors bind.
    • Allosteric Site: where non-competitive, mixed, and uncompetitive inhibitors bind.

Key Concepts

Enzyme Basics

  • Enzymes increase reaction speed and decrease activation energy.
  • Do not change the equilibrium, thermodynamics, or delta G.

Types of Inhibitors

  1. Competitive Inhibitors

    • Bind to the active site.
    • Do not change Vmax (maximum rate of reaction).
    • Increase Km (Michaelis constant), which inversely affects substrate affinity.
    • Can be overcome by increasing substrate concentration.
    • Mnemonic: Cody the Capitalist.
    • Graph Position: Shift right on Michaelis-Menten, intersect y-axis on Lineweaver-Burke.

  2. Non-Competitive Inhibitors

    • Bind to the allosteric site.
    • Decrease Vmax.
    • Do not change Km.
    • Mnemonic: Nancy the Karen.
    • Graph Position: Vmax decreases on Michaelis-Menten, intersect x-axis on Lineweaver-Burke.

  3. Mixed Inhibitors

    • Bind to either the enzyme alone or the enzyme-substrate complex.
    • Vmax decreases.
    • Km may increase or decrease.
    • Distinction: Different affinity for binding states, causing variable effects on Km.
    • Graph Position: Intersect at point neither on x-axis nor y-axis on Lineweaver-Burke.

  4. Uncompetitive Inhibitors

    • Bind only to the enzyme-substrate complex.
    • Decrease both Vmax and Km.
    • Prevents detachment by increasing affinity.
    • Graph Position: Lines are parallel on Lineweaver-Burke.

Graphical Representation

  • Michaelis-Menten Plot

    • Shows reaction rate vs. substrate concentration.
    • Competitive: Right shift.
    • Non-competitive: Decrease in Vmax.

  • Lineweaver-Burke Plot

    • Double-reciprocal plot of enzyme kinetics.
    • Competitive: Intersects y-axis.
    • Non-competitive: Intersects x-axis.
    • Mixed: Intersection off both axes.
    • Uncompetitive: Parallel lines.

Mnemonics for Understanding

  • Cody the Capitalist for competitive inhibitors.
  • Nancy the Karen for non-competitive inhibitors with a mnemonic on x-axis intersection.

Conclusion

  • Emphasizes drawing graphs from scratch for better understanding.
  • Encourages checking out additional pharmacology and toxicology resources available on website.
  • Urges practice and engagement with the content to better grasp the concepts.

For more information, visit medicosisperfectionist.com and explore courses to deepen your understanding of pharmacokinetics and pharmacodynamics.

"Medicine makes sense once you understand what you're talking about." - Medicosis Perfectionalis

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