Overview Enzymes

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Overview Enzymes
2011-10-04 13:13:48
Overview Enzymes

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  1. If the enzyme is a type of kinase, what does it do and what is the cofactor?
    Kinase tends to be a Transferase enzyyme.

    Its cofactor is Magnesium.
  2. What does Metalloenzyme mean?
    Enzymes which require more than one metal ion (cofactors) for catalytic activity.

    1/3 of all enzymes are metalloenzymes.
  3. How much energy is required for molecules to go through a reaction?
    They must contain sufficient energy to overcome the energy barrier of the transition state.
  4. Does the free energy of activation need to be high or low in order for the molecules to have enough energy to pass through the transition state.
    The lower the free energy of activation, the more they have sufficient energy to pass through the transition state.
  5. What happens to the free energies of the reactants and and products after the reaction proceeds with an enzyme.
    The free energies of both of these remains the same.
  6. How does the site where the enzyme bonds with the substrate work?
    It's an active site which changes the substrate, it's a tool, employing a diversity of chemical mechanisms to facilitate the conversion of substrate to product. (Example: bent stick to broken stick).
  7. What does it mean in a reaction which is saturated?
    All of the available binding sites on enzymes are filled with substrate.
  8. What type of saturation curve on a graph do enzymes produce?

    What if it is allosterically controlled.
    Enzymes show a hyperbolic curve, steady slope upward with flat leveling off.

    Allosterically controlled result in a sigmoid curve. S-shaped
  9. What is the optimum temperature for most human enzymes?
    35-40 degrees C
  10. What are ideal values for

    k1 association constant
    k-1-dissociation constant
    k2 time takes to convert ES to product

    To produce product efficiently?
    Ideal for efficiency

    • k1 very big
    • k
    • k2 very small

  11. What are ideal values for efficiency in

    V0= Vmax[S]
    Km + [S]
    • Vo: Large number
    • Vmax: Large number
    • Km: Small number

    Remember Km= (k -1+k2)/k1
  12. What are three required assumptions for deriving the Mechaelis-Menten rate equation?
    • 1. The concentration of the substrate is much greater than the concentration of the enzyme.
    • 2. Rate is determined at the point of steady state (formation of ES is equal to the degredation of ES).
    • 3. Rate is determined at the VERY INSTANT steady state has been achieved.
  13. What is value of Km
    Km is equal to the substrate concentration at which velocity is one-half Vmax

    It is numerically the concentration at which half of the enzymes would be bound to the substrate.
  14. What is the relationship between the Km value and affinity of an enzyme?
    Large Km of enzyme reflects a low affinity of enzyme for the substrate.

    Small Km of enzyme reflects a high affinity of enzyme for the substrate.
  15. What factors will effect reaction velocity?
    1. Substrate concentration: the more substrate the higher the velocity until it reaches saturation with enzyme

    2.Temperature (optimum for human enzymes 35-40 degrees C).

    3. Ph level
  16. What is an enzyme inhibitor?
    What types of inhibitors are there?
    What kinds of bonds do these different types have?
    How does the type of bond influence the reaction.
    Enzyme inhibitor is any substance that can diminish the velocity of an enzyme catalyzed reaction.

    Irreversible inhibitor has a covalent bond

    Reversible inhibitor has a noncovalent bond. This type of bond can be broken through dilution, resulting in recovery of the enzyme activity.
  17. What are the two types of reversible inhibitions and important facts?
    Competitive Inhibition: Inhibitor binds reversibly to the SAME site that the substrate would occupy. This can be reversed by increasing substrate

    Non-competitive Inhibition: Inhibitor binds to the Enzyme at a NON-ACTIVE site, resulting in conformational changes subsequently leading to deficiency in catalytic efficiency.
  18. What are the effects on Maximal velocity, Vmax and Michaelis constant, Km for Competitive and Non-Competitive Inhibition?
    • Competitive Inhibition: Vmax is the same
    • Km is increased

    • Noncompetitive Inhibitor: Vmax is decreased
    • Km is unchanged
  19. What is the kind of biochemical mechanism for about 1/2 of he commonly dispensed drugs in the US?
    They are enzyme inhibitors, such as Lipitor, Lovastatin, is a competitive inhibitor that sits in the substrate cite of HMG-CoA on the enzyme HMG-CoA reductatse.