Download Biochemistry: A Short Course - Chapter 5: Basic Concepts of Enzyme Action - Prof. Yogaraja and more Study notes Biochemistry in PDF only on Docsity! • Biochemistry: A Short Course • First Edition Tymoczko • Berg • Stryer © 2010 W. H. Freeman and Company CHAPTER 5 Basic Concepts of Enzyme Action Enzymes Carbonic anhydrase – fastest enzymes known It adding water to carbondioxide – simple reaction Transfer of corbon dioxide from the tissues to the blood They are highly specific Catalyzes a single reaction or a set of closely related reaction Trypsin - specific -splitting of peptide
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Biochemistry: A Short Course, First Edition
© 2010 W.H. Freeman and Company
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carboxyl side of lysine and arginine residues Thrombin- catalyzes the hydrolysis of Arg-Gly bonds Co factor- two groups 1. Small organic molecules – called coenzymes 2. metals Free energy is useful thermodynamic function for understanding enzymes Thermodynamic properties of a reaction depends on 1. The free energy difference between the products and- reactants-This determine whether the reaction will take place 2. The free energy required to initiate the conversation of reactants in to products - Determine the rate of reaction G = negative reaction take place spontaneously G = positive – reaction cannot take place- input of free energy is required- these reactions are called endergonic G = zero- equilibrium G = provides no information about the rate of reaction Read page 67 and 68 free energy An enzyme cannot alter the law of thermodynamics and consequently cannot alter the equilibrium of a chemical reaction. In this graph – amount of product formed is the same whether or not the enzyme is present , but, in the this example, the amount of product formed in seconds when the enzyme is present might take hours or centuries to form if the enzyme were absent. Read page 69 Enzymes decreases the activation energy The difference in free energy between the transition state and the substrate is called the free energy of activation or simply the activation energy The formation of an enzyme substrate complex is the first step in enzymatic catalysis. Enzymes bring together substrates in enzyme substrate complexes. The substrates are bound to a specific region of enzyme called the active site. Active site is composed of residues that come from different parts of the polypeptide chain The active site of the unbound enzyme is complementary in shape to the substrate – lock and key The enzyme changes shape on substrate binding . The active site forms a shape complementary to the substrate only after the substrate has been bound- induced fit Read page 71 Transition state analogs are potent inhibitors of enzymes The isomerization of L proline to D –proline by proline recemase , a bacterial enzyme , proceeds through a planar transition state in which the alpha carbon is trigonal rather than tetrahedral. Pyrrole 2- carboxylase , a transition –state analogue because of its trigonal geometry , is potent inhibitor of proline
