Enzymes

Introduction

• Enzymes are vital substances that control biochemical reactions in the human body.
• Discovered by Anselme Payen in 1833.
• They can be proteins or ribonucleic acids (RNA).
• Enzymes speed up reactions by modifying substrates.
• They exhibit specificity, binding to specific substrates.

Mode of Action

• Enzymes lower activation energy, facilitating reactions.
• They bind substrates at a specific region called the "Active Site".
• Active sites are unique due to the arrangement of amino acids.

Components

• Active Site: Region where the substrate binds.
• Cofactors: Non-protein parts that enhance enzyme function.
  • Cations: Metal ions that temporarily bind to activate enzymes.
  • Organic Molecules: Vitamins or vitamin products that temporarily join enzyme-substrate complexes.
  • Prosthetic Groups: Permanently bonded to enzymes.
• Holoenzyme = Apoenzyme (inactive protein) + Coenzyme (non-protein).

Models of Enzyme Action

• Lock and Key Hypothesis: Substrate fits into the active site like a key in a lock.
• Induced Fit Hypothesis: Enzyme changes shape to bind the substrate more tightly.

Environmental Effects on Enzyme Function

• Temperature: Optimal at 37°C. Deviations can denature enzymes.
• pH: Affects the amino acids in active sites, extreme pH can denature enzymes.
• Enzyme Concentration: Initially increases reaction rate until saturation.
• Substrate Concentration: Increases reaction rate until saturation.

Inhibition of Enzyme Activity

• Inhibitors: Substances that decrease enzyme activity.
  • Competitive Inhibitors: Block active sites, preventing substrate binding.
  • Non-competitive Inhibitors: Bind elsewhere, altering enzyme shape.

These notes cover the key aspects of enzyme function, structure, and the factors affecting their activity. They provide a comprehensive overview suitable for study and review.