Biochemistry

• BMS1041


  Biochemistry course code
• Metalloproteins


  Proteins that contain metal ions
• [e-mail]


  Lecturer email
• Protein Structure


  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Metalloproteins


  • Bind/orientate ligands & substrates
  • Mediate oxidation-reduction reactions
  • Charge stabilization
  • Promote nucleophilic catalysis
• Ligands


  • Porphyrin
  • Heme
• Soret band


  Absorption peak in ultraviolet and visible range
• Deoxy-Hb


  Hemoglobin without oxygen, 429 nm Soret band
• Oxy-Hb


  Hemoglobin with oxygen, 414 nm Soret band
• The heme group is a strong chromophore that absorbs both in ultraviolet and visible range
• Oxygen binding alters the electronic properties of the heme and shifts the position of the Soret band
• Deoxyhemoglobin (in venous blood) appears purplish/blueish in color and oxyhemoglobin (in arterial blood) is red

  
• Restriction enzymes


  • Endonucleases
• Restriction enzymes


  • Mg2+ to reduce electrostatic repulsion
  • Facilitates orientation

  
• Scissile bond


  Covalent chemical bond that can be broken by an enzyme
• Carboxyglutamate & Calcium


  • Post-translational modification

  
• Alcohol Dehydrogenase (ADH)


  C2H5OH + NAD+ CH3CHO + NADH + H+
• Roles of metals in protein function

  • Bind/orientate ligands & substrates
  • Mediate oxidation-reduction reactions
  • Charge stabilization
  • Promote nucleophilic catalysis
• Reduction of hydrogen peroxide

  O2 -> O2- -> H2O2 -> OH- -> H2O
• Catalase


  Enzyme that catalyses the decomposition of hydrogen peroxide to water and oxygen
• Superoxide dismutase


  Enzyme that catalyses the dismutation of superoxide into oxygen and hydrogen peroxide
• Glutathione Peroxidase & Glutathione Reductase


  Coupled enzyme reaction that reduces hydrogen peroxide
• Cytochrome P-450 monooxygenase system

  1. H + O2 + NADPH + H+ -> R-OH + H2O + NADP+

  
• Mitochondrial system


  Steroids, bile acids, vitamin D
• Microsomal system


  Xenobiotics (drug metabolism)
• ATP and Magnesium


  Mg2+ functions: reduce electrostatic repulsion, orientate substrates
• Aconitase: Isomerization by Dehydration/Rehydration


  Iron-Sulfur Center in Aconitase
• Carbonic anhydrase


  H2O + CO2 ⇌ H2CO3 ⇌ H+ + HCO3-
• Next topic: Enzymes
• Enzyme


  Biological catalyst that specifically binds and chemically transforms other molecules (substrates)
• Ribozyme


  RNA molecule that can have complex tertiary structures and be catalytically active
• Cofactor


  Metal ion or organic molecule needed for enzyme activity
• Coenzyme


  Complex organic molecule needed for enzyme function, often derived from vitamins
• Apoenzyme


  Protein portion of an enzyme, exclusive of any cofactors or prosthetic groups
• Holoenzyme


  Catalytically active enzyme, including all necessary subunits, prosthetic groups, and cofactors
• Enzymes used in industry and agriculture

  • Rennet (cheesemaking)
  • Invertase (soft-centred chocolates)
  • Phytases (animal feed)
• Enzymes are usually proteins and their activity depends on the integrity of their three-dimensional structure
• Many biological reactions are chemically unfavourable so need enzymes
• Enzymes are usually much better (specific and efficient) than catalysts in chemistry
• If human enzymes don't work properly it can lead to disease