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What is the primary function of enzymes in biochemical reactions?
What is the primary function of enzymes in biochemical reactions?
Which of the following enzymes is classified as a hydrolase?
Which of the following enzymes is classified as a hydrolase?
What type of reaction do ligases specifically catalyze?
What type of reaction do ligases specifically catalyze?
What type of reaction do oxidoreductases typically catalyze?
What type of reaction do oxidoreductases typically catalyze?
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Which enzymes are specifically involved in the fermentation of sugar into ethanol?
Which enzymes are specifically involved in the fermentation of sugar into ethanol?
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Which enzyme class is responsible for transferring a chemical group from one compound to another?
Which enzyme class is responsible for transferring a chemical group from one compound to another?
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What do isomerases primarily catalyze?
What do isomerases primarily catalyze?
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In enzyme nomenclature, which suffix is typically added to the name of a substrate to denote an enzyme?
In enzyme nomenclature, which suffix is typically added to the name of a substrate to denote an enzyme?
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Which part of the Enzyme Commission number indicates the functional group upon which the enzyme acts?
Which part of the Enzyme Commission number indicates the functional group upon which the enzyme acts?
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What type of reaction does phosphoglucoisomerase catalyze?
What type of reaction does phosphoglucoisomerase catalyze?
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Study Notes
Enzymes Overview
- Enzymes are biological catalysts primarily composed of proteins.
- They accelerate biochemical reactions without being consumed in the process.
- Enzymes are classified into six main categories: Hydrolases, Oxidoreductases, Lyases, Isomerases, Ligases, and Transferases.
Hydrolases
- Catalyze hydrolysis reactions by adding water to cleave bonds.
- Subdivided into three classes:
- Carbohydrases (e.g., Sucrase, Diastase)
- Proteases (e.g., Pepsin, Trypsin)
- Esterases (e.g., Lipase, Chlorophyllase)
Oxidoreductases
- Catalyze oxidation/reduction reactions by transferring H, O atoms, or electrons.
- Subdivided into four classes:
- Oxidases
- Peroxidases
- Dehydrogenases
- Catalases (e.g., converts hydrogen peroxide into water and oxygen)
Lyases
- Catalyze the breaking of bonds by removal of groups, without adding water.
- Example: Zymase converts sugar into ethanol and carbon dioxide.
- Aldolase is involved in glycolysis and splits fructose-1,6-diphosphate.
Isomerases
- Catalyze geometric or structural changes within a single molecule.
- Example: Phosphoglucoisomerase converts glucose-6-phosphate to fructose-6-phosphate.
Ligases
- Join two molecules by synthesizing new covalent bonds with the breakdown of ATP.
- Examples include Asparagine synthetase and RNA Ligase.
Transferases
- Catalyze the transfer of chemical groups from one compound to another.
- Examples include transaminases (transfer amino groups) and hexokinases (transfer phosphate groups).
Enzyme Nomenclature
- Trivial names (e.g., Pepsin, Trypsin) or suffix "-ase" added to substrates (e.g., Sucrase).
- Reaction type nomenclature also uses "-ase" (e.g., Carboxylase).
- Enzyme Commission (EC) numbering system categorizes enzymes based on class and substrate involved.
Structure of Enzymes
- Two types of protein enzymes:
- Simple Protein Enzymes (consist of protein only).
- Complex (Conjugated) Protein Enzymes (contain protein and non-protein components).
- Apoenzyme (protein part) and Cofactor/Coenzyme (non-protein part).
- Holoenzyme is the complete enzyme.
Cofactors
- Types of cofactors include:
- Prosthetic groups (tightly bound, e.g., FAD).
- Coenzymes (detach from the enzyme post-catalysis, e.g., NAD+).
- Activators (usually metal ions, e.g., Zn²⁺, Ca²⁺).
Enzyme Functionality
- Substrates are reactants that bind to enzymes to form enzyme-substrate complexes.
- The active site is where the substrate binds and catalysis occurs.
- Enzymes remain unchanged post-reaction.
Characteristics of Enzymes
- Needed in small amounts to catalyze larger reactant quantities.
- Sensitive to temperature and pH levels.
- Highly specific for particular reactions.
- Exhibit colloidal nature.
Mechanism of Enzyme Action
- Substrate binds to enzyme's active site forming the enzyme-substrate complex.
- This complex transforms into products, regenerating the original enzyme.
Factors Affecting Enzyme Activity
- Enzyme activity is influenced by:
- Substrate concentration
- Enzyme concentration
- Temperature
- pH levels
- Inhibitors
Temperature and pH Effects
- Rate of reaction increases with temperature until a maximum is reached, after which it declines.
- Each enzyme has an optimal pH for maximum activity; deviations can lower activity or inactivate the enzyme.
Concentration Effects
- Increasing substrate concentration typically increases reaction rate until enzymes are saturated.
- Higher enzyme concentrations yield faster reactions until the substrate becomes limiting.
Inhibitors
- Competitive inhibitors block the active site.
- Non-competitive inhibitors bind elsewhere on the enzyme, reducing its efficiency.
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