ENZYMES

• Catalyst


  Anything that speeds up the rate of the reaction, NOT consumed in a reaction
• Catalysis


  The process of increasing the rate of a chemical reaction through a catalyst
• Enzymes

  Proteins that serve as biological catalysts for reactions in all living organisms, water-soluble, globular proteins
• Enzymes


  • Active Site is a small cavity that contains amino acids that are attracted to the substrate with various types of intermolecular forces

  
• Enzyme-substrate complex formation

  1. Substrate binds on the active site

  2. Enzyme-substrate complex forms when the substrate binds on the active site of the enzyme
• Allosteric site


  A cavity or region found in an enzyme other than the active site where the regulatory molecule (an activator or inhibitor) binds

  
• Types of enzymes

  • Simple
  • Conjugated
• Simple enzyme


  Enzyme is completely made of protein
• Conjugated enzyme


  Enzyme is composed of a protein and non-protein entity

  
• Coenzyme


  An organic or metallorganic molecule that acts as a transient carrier of specific functional groups, needed for an enzyme-catalyzed reaction to occur
• Apoenzyme


  The protein part of a conjugated enzyme
• Cofactor


  A metal ion or nonprotein molecule
• Cofactor


  • Nicotinamine Adenine Dinucleotide
• International Classification of Enzymes

  • Oxidoreductase
  • Transferase
  • Hydrolases
  • Lyases
  • Isomerases
  • Ligases

  
• Oxidoreductase


  Catalyze oxidation-reduction reactions, coenzyme serves as the oxidizing/reducing agent

  
• Oxidoreductase subclasses

  • Oxidases
  • Reductases
  • Dehydrogenases

  
• Transferase


  Catalyze the transfer of a group from one molecule to another
• Transferase subclasses

  • Transaminase
  • Kinase
• Transaminase


  Catalyzes the transfer of an amino group (NH2)

  
• Kinase


  Catalyzes the transfer of a phosphate group (P)
• Hydrolase


  Catalyze hydrolysis reactions
• Hydrolase subclasses

  • Lipase
  • Protease
  • Nuclease
• Lipase


  Catalyze hydrolysis of lipid esters
• Protease


  Catalyze hydrolysis of amide bonds in proteins
• Nuclease


  Catalyze hydrolysis of nucleic acids
• Lyase

  Catalyze the addition of a molecule to a double bond or the elimination of a molecule to give a double bond
• Lyase subclasses

  • Dehydrase
  • Decarboxylase
  • Synthase

  
• Dehydrase


  Catalyze H2O removal

  
• Decarboxylase


  Catalyze CO2 removal
• Synthase


  Catalyze the addition of small molecule to a double bond
• Isomerase


  Catalyze the conversion of one isomer to another, isomerization is the process where the molecule with the same atoms is transformed into another molecule but have a different arrangement
• Ligase


  Catalyze the joining together of two molecules but requires energy to perform the reaction
• Carboxylases


  Bond formation between a substrate and CO2
• Lock-and-Key Model

  • The active site is rigid (cannot alter/adjust), substrate MUST match the shape of the active site for catalysis to happen, HIGH SPECIFICITY in a chemical reaction
• Induced Fit Model


  • The shape of the active site is more flexible, active site adjusts for substrate to fit
• TEMPERATURE

  • An increase temperature increases the rate of reaction
  • Directly Proportional ↑TEMP = ↑RATE OF REACTION
• Optimum Temperature

  • temperature at which enzyme reaches maximum activity (37C) Higher temperature than its optimum temperature can lead to denaturation. At 50-60C, enzymes are completely destroyed
• pH

  • At pH 7.40, catalysis occur at maximum activity
  • Pepsin → Opt. pH of 2.0
  • Trypsin → Opt. pH of 8.0
• ALLOSTERIC CONTROL

  Binding of a regulator to a site on an enzyme that affects the enzyme’s ability to bind a substrate as its active site
• Regulator

  • Allosteric enzyme - changes the shape of the protein