lec15 - Biochemistry I Fall Term, 2004 October 6, 2004...

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1 Biochemistry I Fall Term, 2004 October 6, 2004 Lecture 15: Enzyme Inhibition Key Terms: Competitive inhibition Nonompetitive inhibition Feedback inhibition Allosteric effector Irreversible inhibition Protein phosphorylation Zymogen Links : ( I ) Review Quiz on Lecture 15 concepts ( I ) Data Analysis for Competitive Inhibition The handout shows enzyme inhibition curves. ( I ) Structure of a Trypsin-Inhibitor Complex : "Must-viewing" of an enzyme-inhibitor complex. ( S ) ATCase Architecture with and without bound ATP (activator) and CTP (inhibitor). ( S ) Graphing Quiz: Enzyme Inhibition Kinetics : Determine V max , K M and K I . 5.7 Inhibition of Enzymatic Reactions Studies on Inhibitors are useful for: 1. Mechanistic studies to learn about how enzymes interact with their substrates. 2. Role of inhibitors in enzyme regulation. 3. Drugs if they inhibit aberrant or harmful biochemical reactions: penicillin, ampicillin , et al .: interfere with the synthesis of bacterial cell walls. methotrexate - anti-cancer drug that affects DNA metabolism in actively growing cells viagra - interfers with nitric oxide breakdown (NO is a vasodilator) 4. Understanding the role of biological toxins. Arsenate - mimics phosphate esters in enzyme reactions, but are easily hydrolyzed. Amino acid analogs - useful herbicides ( i.e. roundup) Insecticides - chemicals targeted for the insect nervous system.
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2 A. Competitive Inhibition 1. Inhibitor binds to the same site on the enzyme as the substrate. 2. Inhibitor only binds to the free enzyme. 3. Inhibitor is usually structurally very similar to the substrate. Succinate/Malonate ATP/AMP The reaction scheme that corresponds to competitive inhibition is: The inhibitor reduces the amount of E by the formation of EI complex. The inhibitor does not affect the ES complex after it has formed. The dissociation constant for the inhibitor is K
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This note was uploaded on 03/04/2012 for the course BIOCHEM 451 taught by Professor Clavijo during the Spring '06 term at Carnegie Mellon.

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lec15 - Biochemistry I Fall Term, 2004 October 6, 2004...

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