Enzyme Inhibitors Lecture

Overview

Enzyme inhibitors are substances that can decrease or stop enzyme activity.
Many drugs, such as antibiotics and antivirals, function as enzyme inhibitors.
Types of Enzyme Inhibitors:
- Competitive Inhibitors
- Non-Competitive Inhibitors

Definition: Compete with the substrate for the active site of an enzyme.
Mechanism:
- Directly block the binding of the substrate.
- Example analogy: A pet sitting in your chair prevents you from sitting.
Example:
- Sulfanilamide
  - Competes with para-aminobenzoic acid (PABA) in bacteria.
  - Blocks folic acid synthesis necessary for bacterial DNA, RNA, and protein synthesis.
  - Used in combination with Trimethoprim to target different parts of the folic acid pathway.
  - Effective and inexpensive, especially useful in low-income regions.

Definition: Bind to a site other than the active site (allosteric site), changing enzyme shape and function.
Mechanism:
- Changes the three-dimensional shape of the enzyme, preventing substrate binding.
- Can be reversible or irreversible.
Examples:
- Cyanide
  - Irreversible inhibitor of cytochrome C oxidase in the electron transport chain.
  - Shuts down cellular respiration, acting as a potent poison.
Cellular Use:
- Cells use this inhibition to regulate metabolic pathways through feedback inhibition.

Mechanism:
- The end product of a pathway serves as an inhibitor for an enzyme earlier in the pathway.
- Prevents the synthesis of more product than necessary, conserving energy.
- Analogy: Manufacturing plant stops production when enough products (e.g., hats) are made.
Process:
- Excess end product binds to the allosteric site of the first enzyme in the pathway, altering its shape and stopping production.
- When product levels drop, inhibition is lifted, and production resumes.

Understanding enzyme inhibitors is crucial for developing drugs and understanding cellular regulation.
Next topic to be covered: Redox reactions in metabolism and ATP production.