Agbi Ch6

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Author:
akowalsk
ID:
204078
Filename:
Agbi Ch6
Updated:
2013-03-05 14:50:48
Tags:
biochem wvu agbi
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Description:
Agbi 410 Biochemistry Exam 2 Chapter 6
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  1. Enzyme function?
    • *speed up rxn by lowering activation energy
    • *substrate binds to active site, is modified, then released
    • *enzyme still fcnl, only substrate changed
    • *cofactors and coenzymes can alter fcn
  2. Activation Energy?
    • *difference between ground state and transition state
    • *step with highest activation energy=rate limiting step
  3. Transition state?
    • *Moment when bonds are formed/broken
    • *Metabolic fate decided
  4. Enzyme specificity
    • *when an enzyme acts on a specific substrate to form a specific product
    • *important b/c dont want enzymes affecting any/all rxns
  5. Induced Fit
    • *enzyme conformation change.
    • *NOT lock and key
    • *precise alignment needed
  6. General Acid-Base Catalysis
    • *Molecule other than water acts as e- donor/acceptor during rxn
    • *unstable intermediates formed
    • *enzyme has fcnl group that donates/accepts e- proton to stabilize rxn

    • R-COOH
    • R-NH3+
    • R-SH
    • R-OH
    • R-Ph-OH
    • R-C=CH
    •    /    \
    • HN     NH+
    •      \   /
    •        C
    •        H
  7. Metal Ion Catalysis
    • *Tight bind to enzyms: Fe, Cu, Zn
    • *Loose bind: Mg-ATP

    • 3 Roles:
    • *Orientation  of substrate binding
    • *Red-Ox rxns
    • * Electrostatic stabilization of negative charge
  8. Covalent Catalysis
    • *Nucleophilic group, X, donates e- pair
    • *forms covalent bond with substrate
    • *when X leaves original enzyme reformed
    • *must be faster than uncatalzyed rxn
  9. Enzymatic rate
    • *controlled by ability of substrate/cofactors
    • *slows down as product accumulates and eqlbm approached
    • *enzymes regulated covalently(AMPK, ACC, phosporylation) or noncovalently (allosteric regulation)
  10. Zymogens
    *undergo cleavage to become active at right time
  11. modulator proteins
    • *proteins which bind to enzymes inducing activity
    • *EX: phosphoprotein phoshatase inhibitor-1 (PPI-1)
  12. Enzyme Kinetics
    *an approach to study rate of a given rxn rate that is catalyzed by enzymes
  13. Velocity
    • *amount of product formed and amoun t of substrate consumed per unit of time
    • *d[P]/dt = -d[S]/dt = k[S]
    • *V0: initial portion of rxn
    • *When V0=Vmax/2 --> Km=[S]
  14. Lineweaver-Burk/Double-Reciprocal Plot
    • 1/V0 = Km/Vmax[S] + 1/Vmax
    •   ( y   =         mx         +     B )

    • y-axis: 1/V0     y-int: -1/Km
    • x-axis: 1/[S]   x-int: 1/Vmax
  15. kcat equations
    kcat = Vmax/[Et]

    V0 = kcat[Et][S] / Km+[S]
  16. Enzyme inhibition
    • Reversible: interact thru noncovalent association/dissociation rxns --> FOCUS
    • Irreversible: cause stable, covalent alternations in enzyme
  17. Reversible inhibition
    • Competitive: S and i compete for active site
    •   *EiS not possible b/c competition
    •   *V0=Vmax[S]/Km(1+[i]/Ki)+[S]
    •   *as [i] incr, V0 decr, Km incr
    •   *Vmax unchanged, Km changes
    • Noncompetitive: interact with E and ES, doesnt bind to active site
    •   *Km unchanged, Vmax changes
  18. Allosteric regulation of enzyme activity
    • *doesn't bind to active site
    • *can alter enzyme conformation

    Ex: phophofructokinase

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