Ch 9.0

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Ch 9.0
2014-10-11 08:56:37
Test Two
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  1. ·         The four classes of enzymes: __(4)__
    ·         Each class catalyzes the reactions that require __. The mechanisms of these enzymes have been revealed through the use of incisive experimental probes, including the techniques of __ and __
    serine proteases, carbonic anhydrases, restriction endonucleases, and myosins

    the addition of water to a substrate

    protein structure determination and site-directed mutagenesis
  2. ·         Each develops strategies to solve a certain problem:

    1) serine proteases
    o   Serine proteases: the challenge is to promote a reaction that is almost immeasurably slow at neutral pH in the absence of a catalyst
  3. ·         Each develops strategies to solve a certain problem:

    2) carbonic anhydrases
    o   Carbonic anhydrases: the challenge is to achieve a high absolute rate of reaction, suitable for integration with other rapid physiological processes
  4. ·         Each develops strategies to solve a certain problem:

    3) restriction endonucleases
    o   Restriction endonucleases: the challenge is to attain a high degree of specificity 
  5. ·         Each develops strategies to solve a certain problem:

    4) myosins
    o   Myosins: the challenge is to utilize the free energy associated with the hydrolysis of ATP to drive other processes
  6. ·         These groups are families; and class members have evolved and been refined
    ·         Binding energy serves two purposes: 

    What are the two?
    • o   It establishes substrate specificity and increases catalytic efficiency
    • o   It also promotes structural changes in both the enzyme and the substrate that facilitate catalysis, called induced fit
  7. Establishment of substrate specificity

    §  Only the__ can participate in most/all of the interactions with the enzyme and thus __, accounting for the exquisite substrate specificity exhibited by many enzymes
    §  the full complement of such interactions is formed only when the __ is __

    ·         interactions between enzyme and substrate __, lowering the __
    • correct substrate
    • maximize binding energy
    • combo of enzyme and substrate
    • in the transition state
    • stabilize the transition state
    • free energy of activation
  8. ·         Enzymes employ one or more strategies for catalyzing specific reactions
    What are the strategies?
    covalent catalysis

    general acid-base catalysis

    catalysis by approximation

    metal ion catalysis
  9. Covalent catalysis
    o   active site has the reactive group (usually a nucleophile), that becomes temporarily covalently attached to a part of the substrate in the course of catalysis
  10. o   General acid-base catalysis: __
    a molecule other than water plays the role of a proton donor or acceptor
  11. Catalysis by approximation
    o   many reactions include two distinct substrates, including all four classes of hydrolases. In such cases, the reaction rate may be considerably enhanced by bringing the two substrates together along a single binding surface on an enzyme
  12. Metal ion catalysis: o   metal ions function catalytically in several ways. What are the three?
    • §  A metal ion can facilitate formation of nucleophiles by direct coordination
    • §  It can serve as an electrophile, stabilizing a negative charge on a reaction intermediate
    • §  Can serve as a bridge between enzyme and substrate, increasing the binding energy and holding the substrate in a conformation appropriate for catalysis
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