Lecture Notes: Enzyme Kinetics and Michaelis-Menten Equation

Introduction

• Biochemistry playlist continuation.
• Previous discussions included enzyme properties, nomenclature, classes, and mechanisms.
• Focus today: Enzyme kinetics and Michaelis-Menten equation.

Enzymes Overview

• Most enzymes are proteins and act as catalysts.
• Catalysts increase reaction rates by lowering activation energy.
• Enzymes do not change equilibrium or overall free energy.
• Key Concepts: Rate/Speed/Velocity (V)

Enzyme Specificity and Affinity

• Enzymes are specific to reactions and substrates (affinity).
• Example: Urease enzyme specifically acts on urea.
• Enzymes form enzyme-substrate complexes.

Enzyme-Substrate Interaction Models

• Key and Lock Theory: Simple specificity model.
• Induced Fit Theory: More accurate model, involving conformational changes.

Enzyme Graphs and Relationships

• Direct Relationship: As substrate concentration increases, reaction rate increases.
• Inverse Relationship: Explained using equations and graphs.
• Saturation: Enzyme activity levels off due to saturation.

Michaelis-Menten Equation

• V (Velocity): Rate of reaction.
• Vmax: Maximum rate of reaction, theoretical.
• Km (Michaelis-Menten Constant): Substrate concentration at half Vmax.
• Km is inversely related to enzyme affinity.

Graph Interpretation

• Shifts in graphs illustrate changes in Vmax and Km:
  • Upward Shift: Increased Vmax, more enzymes.
  • Downward Shift: Decreased Vmax, fewer enzymes.
  • Left Shift: Decreased Km, increased affinity.
  • Right Shift: Increased Km, decreased affinity.

Practical Implications

• Saturation: Similar to facilitated diffusion, enzymes can become saturated.
• Examples: SGLT2 in kidneys, glucose transport.

Historical Reference

• Ancient Egyptian pregnancy test used glucose in urine as an indicator.

Upcoming Topics

• Linweaver-Burk Plot: Reverse relationship interpretation.
• Additional resources and courses on biochemistry and physiology available.

Conclusion

• Recap of key points and encouragement to review materials and graphs.
• Mention of courses and discounts available on Medicosis Perfectionatus website.