Enzymes Overview

Enzymes

• Enzymes are proteins, with a few exceptions being RNA.
• They accelerate reactions significantly, enabling reactions to occur many millions of times faster than without the enzyme.
• Each enzyme typically catalyzes a single reaction.
• Enzymes often require cofactors or coenzymes to function.
• Enzyme function is highly sensitive to environmental factors, including pH, temperature, and substrate concentration and the presence of cofactors.
• Many enzymes are crucial for life, as most biological processes require enzyme assistance.
• Enzymes are found in various cellular locations: nucleus, cytoplasm, mitochondria, and extracellularly.
• Enzyme levels in the bloodstream can indicate cell damage or disease.
• Enzymes play a vital role in both diagnosing and treating diseases.

Enzyme Properties

• Most enzymes are proteins.
• They are sensitive to changes in pH and temperature.
• Enzymes act as catalysts, accelerating reactions without being consumed in the process.
• Enzymes are highly efficient, often increasing reaction rates by several orders of magnitude.
• Enzymes exhibit high specificity, typically working on a single substrate or a narrow group of related substrates.
• Enzymes possess active sites for substrate binding and subsequent product formation.

Types of Enzymes

• Simple enzymes are composed solely of protein.
• Conjugated/Complex enzymes combine a protein portion (apoenzyme) with a non-protein component (cofactor).
  • The complete conjugated enzyme is referred to as a holoenzyme.
• Cofactors include metals (iron, zinc, calcium, magnesium) and non-protein organic molecules called coenzymes (often vitamins or vitamin derivatives such as NAD+, FAD, and NADP+).

Naming Enzymes

• Enzymes are named by adding the suffix "-ase" to the substrate's name or a description of the catalyzed reaction.
• For example, pyruvate dehydrogenase catalyzes the decarboxylation of pyruvate.

Where Enzymes are Found

• Some enzymes are found outside cells, such as digestive enzymes.
• Others are located within cells, in the nucleus, mitochondria, or cytoplasm, depending on their specific function.

Enzyme Concentration

• Enzyme concentration is not fixed, fluctuating based on individual bodily conditions.
• Enzyme concentration may increase in response to higher substrate levels or increased demand.
• Enzyme concentration can decrease due to inhibition mechanisms.

Enzyme Classification

• Enzymes are categorized based on the type of reaction they catalyze.
• Six major classes of enzymes:
  • Oxidoreductases: Catalyze oxidation-reduction reactions.
  • Transferases: Catalyze the transfer of functional groups.
  • Hydrolases: Catalyze hydrolysis reactions, breaking bonds with water.
  • Lyases: Catalyze the breaking of bonds without hydrolysis or oxidation.
  • Isomerases: Catalyze the rearrangement of atoms within a molecule.
  • Ligases: Catalyze the joining of two or more molecules.

Enzyme Specificity

• Enzymes display specificity, catalyzing reactions with specific substrates.
• Enzyme specificity categorizations:
  • Absolute specificity: The enzyme works only with a single substrate for a particular reaction.
  • Group specificity: The enzyme works with a particular functional group.
  • Linkage specificity: The enzyme works on a specific type of chemical bond.
  • Stereospecificity: The enzyme works on a specific stereoisomer.

How Enzymes Work

• Enzymes bind substrates at specific active sites.
• Active sites have unique shapes and chemical environments for substrate binding.
• Once bound, enzymes facilitate reactions by:
  • Lowering the activation energy, facilitating reaction pathways.
  • Stabilizing the transition state, making reaction progress easier.

Enzyme Inhibition

• Enzyme inhibition occurs when a molecule hinders enzyme activity.
• Two major types of enzyme inhibition:
  • Competitive inhibition: The inhibitor competes with the substrate for the active site.
  • Non-competitive inhibition: The inhibitor binds to a site other than the active site, altering the enzyme's shape and hindering its function.

Examples of Important Enzymes

• Urease: Breaks down urea.
• Pepsin: Breaks down proteins in the stomach.
• Trypsin: Breaks down proteins in the small intestine.
• Chymotrypsin: Breaks down proteins in the small intestine.
• Lactase: Breaks down lactose in the small intestine.
• Amylase: Breaks down starches in the mouth and small intestine.
• Lipase: Breaks down fats in the small intestine.
• Pyruvate dehydrogenase: Involved in glucose breakdown.
• Acetylcholinesterase: Breaks down the neurotransmitter acetylcholine.

Explore the fascinating world of enzymes, the specialized proteins that catalyze reactions at remarkable speeds. Learn about their sensitivity to environmental conditions, their roles in cellular functions, and their significance in diagnosing diseases. This quiz covers essential characteristics and properties of enzymes.