Enzyme Basics and Rates

Enzyme Basics and Rates: Introductory Lecture Notes

Introduction to Enzymes

  • Definition: Enzymes are proteins that catalyze specific reactions essential for physiological functions.

    • They accelerate biochemical processes without being consumed.

    • Examples of catalyzed functions include hydration of carbon dioxide, nerve conduction, muscle contraction, nutrient breakdown, and energy utilization.

  • Location and Clinical Significance:

    • Found in all body tissues.

    • Released from specific sites after cell injury, making them useful diagnostic markers.

    • Examples: Liver enzymes indicate liver disease; pancreatic enzymes indicate pancreatic issues.

    • Used to diagnose specific diseases, physiological abnormalities, and certain inborn errors of metabolism (where dangerous metabolites might accumulate).

    • Important for certain coagulation factors, measured in the coagulation department.

Enzyme Nomenclature

  • Common Naming Conventions:

    • Substrate-based: Name of the substrate with an "-ase" suffix.

      • Example: Lipase breaks down lipids; Amylase breaks down starches.

    • Reaction-based: Named for the type of reaction catalyzed.

      • Example: Lactate Dehydrogenase (LDH or LD) indicates a dehydrogenation reaction.

    • Systematic Names: Provide details on the substrate, catalyzed reaction, and sometimes the coenzyme.

      • Example: Carbonic anhydrase.

    • Trivial or Recommended Names: Traditional names for some enzymes.

      • Examples: Trypsin, Pepsin.

    • International Board of Chemistry (IBC) Numeric Code: A specific numeric code for enzymes (not essential to memorize, but useful for recognition).

Enzyme Classification: The Six IUBMB Classes

Enzymes are categorized into six major classes based on the type of reaction they catalyze:

  1. Oxidoreductases: Catalyze oxidation and reduction reactions (transfer of electrons or hydrogen).

  2. Transferases: Catalyze the transfer of a group from one molecule to another.

  3. Hydrolases: Catalyze hydrolysis reactions, breaking bonds by adding water.

  4. Lyases: Catalyze the removal of groups from substrates by mechanisms other than hydrolysis (e.g., breaking C-C, C-O, C-N, C-S bonds without water).

  5. Isomerases: Catalyze the interconversion of isomers (molecules with the same chemical formula but different structural arrangements), essentially rearranging atoms within a molecule. (Think of it as