生物反应工程：Chap2_Enzyme_1幻灯片.pptVIP

Enzyme Chapter 2 Enzymes §2.1 Introduction Definition Characteristics Example: Enzymes are named by adding the suffix –ase to the: End of the substrate Such as urease The reaction catalyzed Such as alcohol dehydrogenase EC (Enzyme Commission) SIX classes numbered in FOUR digits Some Examples of Enzyme Alcohol Dehydrogenase EC 1.1.1.1 Glucose Oxidase EC 1.1.3.4 Catalase EC 1.11.1.6 Tryptophan 2,3-dioxygenase EC 1.13.11.11 Pyruvate Kinase EC 2.7.1.40 Creatine Kinase EC 2.7.3.2 Alpha-amylase EC 3.2.1.1 Chitinase EC 3.2.1.14 Oxaloacetate Decarboxylase EC 4.1.1.3 Lactate Racemase EC 5.1.2.1 Ribose Isomerase EC 5.3.1.20 Acetate—CoA Ligase EC 6.2.1.1 Glutathione Synthase EC 6.3.2.3 §2.2 How Enzymes Work? Lock and Key Model Developed by Emil Fischer in 1895. The enzymes and substrates combine because they have complementary molecular geometries. An Example of Lock-Key Model §2.3 Enzyme Kinetics * * Reduced DsbA from E. coli Lysozyme History Büchner, 1897: A breakthrough in Enzymology. Catalysts at work in a living organism could also function completely independently of any life process. Efforts to isolate and purify individual enzymes were Büchner’s discoveries. Sumner, 1926: First isolation of a pure enzyme. Enzymes are usually proteins of high molecular weight (15,000 MW several million Daltons) that act as catalysts. Three-dimensional structure of the folded protein, determined by the sequence of the amino acids. Fragile: mild temperature, pressure, pH, ion strength (ambient conditions). Lower the activation energy of the reaction, but Doesn’t affect Free-energy change Equilibrium constant The decomposition of hydrogen peroxide(H2O2): 18kcal/mol Uncatalyzed reaction at 20 ℃ Colloidal platinum Chemically catalyzed Hydrogen peroxidase Enzymatically catalyzed 13kcal/mol 7kcal/mol From Arrhenius equation: We have, The interaction between the enzyme and its substrate——weak force: van der Waals forces Hydrogen bonding Specific: C