Enzymes: Core Concepts & Kinetics

Enzymes: Core Concepts & Kinetics

• Enzymes are powerful biological catalysts that enhance and control chemical reaction rates dramatically.
• Most enzymes are proteins, enabling specific binding with a wide range of molecules.
• Enzymes accelerate reactions by factors exceeding a billion times and are crucial for reactions that would otherwise occur slowly.
• Example: Carbonic anhydrase hydrates 10^6 molecules of CO2 per second, catalyzing reactions 10^7 times faster than in the absence of the enzyme.

Specificity of Enzymes

• Enzymes exhibit high specificity for the reactions they catalyze and the substrates they bind.
• Proteases, for example, hydrolyze peptide bonds, demonstrating specificity in enzyme activity.
• Various proteolytic enzymes differ in specificity:
  • Papain: Non-discriminating, cleaves any peptide bond.
  • Trypsin: Specific for peptide bonds adjacent to Lysine and Arginine residues.
  • Thrombin: Highly specific for Arg-Gly bonds in particular sequences.

Enzyme Classification and Nomenclature

• Enzyme names often bear little resemblance to their function; many are named after substrates with the suffix "-ase."
• Enzyme classification uses a systematic approach with a four-number code preceded by "EC."
• Key groups in enzyme classification include transferases, hydrolases, and others based on the type of reaction catalyzed.

Cofactors in Enzyme Activity

• Many enzymes require cofactors for activity, which can be metals or coenzymes (small organic molecules).
• An "apoenzyme" is an inactive enzyme without its cofactor, while a "holoenzyme" is the active form, including the cofactor.
• Cofactors can be:
  • Tightly bound coenzymes (prosthetic groups) that remain unchanged during reactions.
  • Loosely associated coenzymes that act like co-substrates.

Energy Transformation by Enzymes

• Enzymes play a crucial role in energy conversion in biochemical reactions, such as in photosynthesis and cellular respiration.
• Photosynthesis transforms light energy into chemical-bond energy.
• Cellular respiration converts free energy in small molecules into ATP, employing enzymes for efficient energy conversion.

Summary Points

• Enzymes are primarily protein-based with significant catalytic power and specificity.
• They enhance reaction rates dramatically and often require cofactors for complete activity.
• Enzymes transform energy efficiently and can be identified through their systematic nomenclature.