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17 - Lecture 17 Introduction to enzymes Monday Enzymes are...

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Unformatted text preview: Lecture 17: Introduction to enzymes Monday, August 23, 2010 Enzymes are proteins that serve to CATALZE a specific chemical reaction or set of reactions. They differ from the chemical catalysts that you saw in organic chemistry in several key respects: 1. Higher reaction rates : A typical enzyme can catalyze a reaction by 10 6 to 10 12-fold over the non-catalyzed reaction-much better than chemical catalysts. 2. Mild reaction conditions : physiological conditions vs. extreme temperatures, pH’s or pressures for chemical catalysis. Monday, August 23, 2010 3. Greater specificity : Synthesis of products occurs with virtually no side products in enzymatically-catalyzed reactions vs. chemical reactions that typically produce many side-products, limiting the yield. Included in this is almost complete STEREOCHEMICAL specificity vs. chemical catalysis which tend to be stereoselective at best. 4. Capacity for regulation: There exist a number of mechanisms by which enzymatically catalyzed reactions can be regulated, via product feed-back inhibition, covalent modification (phosphorylation, for example) or allosteric control. These properties make enzymes remarkable catalysts which are able to very precisely control the chemical reactions that occur in the living cell. Monday, August 23, 2010 STEREOSPECIFICITY: the product of an enzymatically catalyzed reaction will be one enantiomer or the other, if it contains a chiral center: This is because the enzyme’s surface only recognizes one enantiomer of the substrate. Even pro-chiral sites can be discriminated between by an enzyme: Monday, August 23, 2010 The enzyme generally has a geometrical complimentarity...
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17 - Lecture 17 Introduction to enzymes Monday Enzymes are...

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