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Enzymes - Coggle Diagram

- - - - proton transfer from an acid lowers free energy of a reaction's transition state
    - - rate increased by proton abstraction by a base
    - - Simultaneously subject to general acid and gen. base reactions
    - - Asp
      - Glu
      - His
      - Cys
      - Tyr
      - Lys
  - - - Elimination of catalyst reaction which is the reverse of stage 1.
      - Withdrawal of electrons from reaction center by the now electrophilic catalyst
      - nucleophilic reaction to form a covalent bond
  - - - Contain tightly bound metal ion cofactors eg. Fe2+
    - - Bind to substrates to orient them properly
      - mediating Redox reactions through reversible changes in metal ion's oxidation state
      - Electrostatically stabilizing or shielding negative charges
  - - - Stable molecules which resemble transition state geometrically and electronically.
- - - - N-acetylmuramic acid (NAM
      - to
      - N-acetylglucosamine (NAG)
  - - - Resonance-stabilized carbocation.
      - Must be coplanar with its C, O and H atoms
      - Adds ater to regenerate the acid catalyst
    - - Glu 35
      - Asp 52
      - These are side chains which are disposed to either side of glycosidic linkage to be cleaved
    - - Enzyme attaches to bacterial cell wall by binding to hexasaccharide unit
      - Glu 35 transfers its proton to the O1 atom bridging the D and E rings, facilitating cleavage of the C1-O1 bond
      - Asp 52 carboxylate group attacks C1 of the D ring to facilitate covalent catalysis
      - Water replaces the E-ring product in active site
      - Hydrolysis of covalent bond with assistance of Glu 35
- - - - Temperatures below 100 degreesC, neutral pH
    - - Allosteric control
      - Covalent modification
      - Variation of the amounts of enzymes synthesized
  - - - Undergo conformational change on substrate binding
    - - Enzymes have inherent chirality
      - Form asymmetric active sites
  - - - Must be regenerated (return to its original state
    - - only transiently associated with given enzyme molecule
      - NAD+
      - NADP+
    - - Associated with their protein through covalent bonds
      - Eg. heme prosthetic group bound proteins called cytochromes
    - - Catalytically active enzyme-cofactor complex
      - apoenzyme - inactive
      - apoenzyme+ cofactor <=> holoenzyme
- - - - Reactants generally approach each other along path of minimum free energy
      - Plot of free energy versus reaction coordinate = reaction coordinate diagram
      - A+B->transition state -> P+Q
        
        A+B reactants
        
        P+Q products
- - - - Electrostatic catalysis