web_L27_08BIO311C - BIO 311C March 28, 2008 Induction or...

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BIO 311C March 28, 2008
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A D B C E 1 E 2 E 3 Induction or Repression Repression is a decrease in the concentration of enzymes E 1 , E 2 and E 3 . Induction is an increase in the concentration of enzymes E 1 , E 2 and E 3 . * Repression or induction can result from cellular regulation of transcription, post- transcriptional processing or translation, any of which may affect the concentration of functional enzymes. Typically the concentrations of all enzymes of a metabolic pathway are controlled together as a unit.
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A D B C E 1 E 2 E 3 In a separate set of processes (not considered here), the rate of destruction of functional enzymes is also regulated in cells. * For the metabolic pathway shown, the higher the concentrations of Enzymes E 1 , E 2 and E 3 , the faster initial reactant A can be converted to final product D (providing that ample "A" is available).
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A D B C E 1 E 2 E 3 Activation/Inhibition is a set of processes that control how rapidly the enzyme catalyzing the first reaction of a metabolic pathway can function. enzyme that catalyzes the first reaction In addition to its active site for binding substrate A, Enzyme E 1 has one or more allosteric (regulatory) sites to which a an allosteric affector can bind. When the allosteric affector binds to E 1 , then the rate of catalysis of the reaction A B is altered, so the rate of production of substrate B is altered. That, in turn, causes altered (inhibited or activated) production of substrate C and final product D. *
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Feedback Inhibition An Example of Allosteric Regulation In this metabolic pathway, final product D is an allosteric inhibitor of Enzyme E 1 . At low concentrations final product D does not bind to E 1 . But when D accumulates to high concentrations, it effectively binds to an allosteric site on E 1 , inhibiting its function. That causes a slowdown or stoppage of production of B and all later substrates leading to final product D.
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This note was uploaded on 09/28/2008 for the course BIO 311C taught by Professor Satasivian during the Spring '08 term at University of Texas at Austin.

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web_L27_08BIO311C - BIO 311C March 28, 2008 Induction or...

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