Chapter 6a students - Enzymes usually proteins (except...

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Enzymes usually proteins (except small RNAs ribozymes) specific 3D-structure to form specific active site (catalytic center) often require cofactors for activity 1 MCDB310 – Chapter 6: Enzymes
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Some Definitions Apoenzyme + Cofactor Holoenzyme (inactive) (active) 2 MCDB310 – Chapter 6: Enzymes Cofactor: Non-protein component of enzyme required for activity Coenzyme : Cofactor is complex organic molecule Prosthetic group: Cofactor is tightly or covalently bound (e.g. heme in Hb)
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Examples for Metal Ions as Cofactors 3 MCDB310 – Chapter 6: Enzymes
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4 MCDB310 – Chapter 6: Enzymes Examples of Coenzymes
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EC Classification of Enzymes Classification is based on the reaction an enzyme catalyzes: 1. Oxidation/reduction: Oxidoreductases /dehydrogenase 2. Group transfer reactions: Transferases 3. Making and breaking bonds: Hydrolases 4. Lyases 6. Ligases 5. Rearrangements: Isomerases 5 MCDB310 – Chapter 6: Enzymes
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Enzymes as Catalysts can accelerate chemical reactions 10 6 -10 12 times use much milder reaction conditions than chemical catalysis much greater specificity than chemical reactions (e.g. peptide synthesis) degree of activity can be regulated 6 MCDB310 – Chapter 6: Enzymes
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G’ 0 : free energy change under biochemical standard conditions (298 K, 101 kPa, pH 7.0) 7 MCDB310 – Chapter 6: Enzymes Energy Profile of a Chemical Reaction G : free energy of activation
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Active site (catalytic center): Provides favorable microenvironment for reaction, e.g. by: aligning the reacting groups stabilizing charges rearranging bonds stabilizes transition state 8 MCDB310 – Chapter 6: Enzymes The Catalytic Center of an Enzyme
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9 MCDB310 – Chapter 6: Enzymes
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Active site assumes a transition state complementing conformation: 1. substrate binds with a subset of interactions to the active site 2. substrate undergoes conformational changes to assume transition state, which binds even stronger to the active site 3. energy for conformational changes derives from the binding energy (released with every new interaction made) 10 MCDB310 – Chapter 6: Enzymes
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11 MCDB310 – Chapter 6: Enzymes Catalytic Antibodies Antibodies made against transition state analogs
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This note was uploaded on 04/05/2009 for the course MCDB 310 taught by Professor Walter during the Spring '09 term at University of Michigan.

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Chapter 6a students - Enzymes usually proteins (except...

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