enzymes

• Define Enzymes

  Biological catalyst and globular protein that increases the rate

  
  

  Stabilizes the transition state lowering activation energy
• Highly specific to a singular compount


  Urease
• Highly specific to multiple bonds/compounds


  trypsin= peptide bonds
• Change a functional group from one to another


  liver alcohol dehydrogenase
• Types of enzymes in dentistry

  Pellicle proteins eg- a-amylase, lysozyme

  
  

  Saliva proteins eg- carbonic anhydrase and lipase
• Define Activation Site

  Substrate binds through intermolecular forces during a reaction on the surface of an enzyme
• 5 Amino Acids making up enzymes

  Histidine and Arginine (Basic)

  Aspartic acid and Glycine (acidic)
• Classifying Enzymes

  1. Oxidoreductases

  2. Transferases

  3. Hydrolases

  4. Lyase (addition or removal of double bond)

  5. Ligase (joining of two substates using ATP)

  6. Isomerase
• Define Lock and Key Model

  Substrate (key) fits the active site (lock)
• Define Induced Fit Model

  Substrate approaches enzyme, sense and adapts to perfectly fit
• 4 main enzyme mechanics

  1. Proximity effect

  2. Acid Base Catalysis

  3. Electrostatic interactions

  4. Structural Flexibility
• What is step 1 of michaelis-Menton Mechanism?

  E + S = ES

  (fast and reversible)
• What is step 2 of michaelis-menton mechanism?

  ES = E + P

  (RDS)
• Define Cofactors


  non-protein component of enzyme
• Apoenzyme


  Protein component of enzyme
• Holoenzyme


  Combination of both apoenzyme and cofactor
• Substrate


  compound reacting with enzyme
• Active Site


  Substrate fits during a reaction on the surface of an enzyme
• Active Site characteristics


  1. Acidic and basic side chains

  2. Hydrophobic pockets

  3. Shape and polarity

  4. Packing substrates into active site
• Proenzyme


  also known as zymogen

  inactive form of an enzyme that must have protein chain open

  eg: trypsin
• Protein modification


  Changing activity by covalently modifying

  eg: pyravte kinase by phosphorylation
• What is turnover number?


  number of catalytic events at activation site

  
  

  vmax/ enzyme concentration
• k cat


  rate constant measure per second
• v max


  maximum reaction velocity
• What influences enzyme activity?

  1. enzyme concentration

  2. substrate concentration

  3. temperature

  4. pH

  5. presence of cofactors
• Enzyme control- activation


  initiating or increasing the activity of enzymes

  (positive modulation)
• enzyme control- allosteric


  on enzyme but not at active site

  both positive and negative modulations
• enzyme control- inhibition


  less active or inactive

  (negative modulation)
• Competitive inhibitor


  binds to active site so substrate can't = irreversible
• non- competitive inhibitor


  doesn't attach to active site but changes it
• reversible


  allosteric and controls activity