chapter14

chapter14 - BCH 4053 Summer 2001 Chapter 14 Lecture Notes...

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Chapter 14, page 1 BCH 4053 Summer 2001 Chapter 14 Lecture Notes Slide 1 Chapter 14 Enzyme Kinetics Slide 2 Enzyme Characteristics • Catalytic Power • Rate enhancements as much as 10 14 • Specificity • Enzymes can distinguish between closely related chemical species • D and L isomers cis and trans isomers • Diastereomers (glucose and galactose) • Regulation • Ability to activate or inhibit enzymes can control which reactions occur and when. An example of specificity is illustrated by the enzyme fumarase which catalyzes addition of water to the double bond of fumaric acid to form L-malic acid . The isomer of fumarate, maleic acid, does not work. Neither does D-malic acid, the enantiomer of L-malic acid. Slide 3 Enzyme Terminology • Substrates • Substances whose reaction is being catalyzed • Products • End products of the catalyzed reaction • For reversible reaction, designation depends on point of view. • A + B & P + Q • A, B products, P, Q reactants, or vice versa An enzyme is a catalyst, and as such does not influence the equilibrium position of the reaction—only its rate. So one can start with A and B and get P and Q formed, but one can also start with P and Q and get A and B formed.
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Chapter 14, page 2 Slide 4 Enzyme Nomenclature • Some names are historical common names • Trypsin, chymotrypsin, • Some have common names related to the substrate(s), usually ending in –ase . • urease, protease, ribonuclease, ATPase, glucose-6-phosphatase • All enzymes have a systematic name based on international agreement Slide 5 Systematic Classification of Enzymes • 1. Oxidoreductases • 2. Transferases • 3. Hydrolases • 4. Lyases • 5. Isomerases • 6. Ligases Slide 6 Oxidoreductases • Catalyze transfer of electrons between species (i.e., oxidation and reduction) • Some are called dehydrogenases in their common name. • Some are called oxidases or reductases . • Often coenzymes such as NAD, NADP, FAD, or a metal ion is involved in the reaction.
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Chapter 14, page 3 Slide 7 Transferases • Catalyze transfer of a functional group from one molecule to another • e.g., phosphate groups, methyl groups, acyl groups, glycosyl groups, etc. • Enzymes catalyzing transfer of a phosphate from ATP to another acceptor are commonly referred to as kinases . Slide 8 Hydrolases and Lyases Hydrolases catalyze hydrolysis of a chemical bond • Includes proteases, esterases, phosphatases, etc. Lyases catalyze reversible addition of groups to a double bond. • Usually H 2 O or NH 3 added • Interconversion of fumaric acid and L-malic acid which we alluded to earlier. Slide 9 Isomerases and Ligases Isomerases catalyze Conversion of one isomer to another. • The only enzyme class in which a single substrate and product is involved.
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This note was uploaded on 05/22/2011 for the course BCH 4053 taught by Professor Logan during the Fall '06 term at FSU.

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chapter14 - BCH 4053 Summer 2001 Chapter 14 Lecture Notes...

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