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Bài giảng Kỹ thuật phản ứng sinh học: Chương 2 - Bùi Hồng Quân

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Bài giảng Kỹ thuật phản ứng sinh học: Chương 2 Động học phản ứng enzyme, cung cấp cho người học những kiến thức như: Các khái niệm cơ bản; Xúc tác sinh học; Phương trình Michelis Menten; Động học phản ứng enzyme. Mời các bạn cùng tham khảo!

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http://buihongquan.com Chương 2. Động học phản ứng enzyme  2.1. Cá c khá i niệ m cơ bả n  2.2. Xú c tá c sinh họ c  2.3. Phương trình Michelis Menten  2.4. Đọ ng họ c phả n ứng enzyme 12/23/2018 Bioreaction engineering. 80
http://buihongquan.com QUIZ 1. What is enzyme? 2. What is the function of enzyme? 3. What are the special characteristics of enzyme? 4. What kind of binding energy involve for the formation of ES complexes (enzyme-substrate complex)? 5. Define these terms: Active site Activation energy Cofactors Apoenzyme Holoenzyme Coenzyme Substrate 12/23/2018 Bioreaction engineering. 81
http://buihongquan.com QUIZ • What characteristic features define enzymes? • Can the rate of an enzyme-catalyzed reaction be defined in a mathematical way? • What equations define the kinetics of enzyme- catalyzed reactions? • What can be learned from the inhibition of enzyme activity? • What is the kinetic behavior of enzymes catalyzing bimolecular reactions? • How can enzymes be so specific? • Are all enzymes proteins? • Is it possible to design an enzyme to catalyze any desired reaction? 12/23/2018 Bioreaction engineering. 82
http://buihongquan.com Role of Bioprocess Engineering  exploit advances in biology to create new products  design biochemical processes & operate plants  develop energy resources  Develop new, environmentally friendly, and safer processes to make the biochemical products that people depend on.  Work in research and development laboratories, creating polymeric materials with improved performance and durability.  Work in manufacturing, making vaccines and antibiotics.  Invent new ways to keep our food and water supplies safe. 12/23/2018 Bioreaction engineering. 83
http://buihongquan.com Bioprocess Engineer’s Task  Minimize production of unwanted byproducts  Separate the good (product) from the bad (byproducts)  Recover the unused reactants  Maximize profit, minimize energy consumption  Minimize impact on the environment 12/23/2018 Bioreaction engineering. 84
http://buihongquan.com OUTLINE  Introduction  Enzyme Structure  Enzyme Function  Enzyme Kinetics  A)Michaelis –Menten Kinetics  B) The Rapid Equilibrium Assumption  C) The Quasi-Steady-State Assumption 12/23/2018 Bioreaction engineering. 85
http://buihongquan.com Enzymes  There are many chemical compounds in the living cell.  How they are manufactured and combined at sufficient reaction rates under relatively mild temperature and pressure?  How does the cell select exactly which reactants will be combined and which molecule will be decomposed? Catalysis by ENZYME 12/23/2018 Bioreaction engineering. 86
http://buihongquan.com Enzymes •Enzymes are biological catalysts that are protein molecules in nature- react in mild condition •They are produced by living cells (animal, plant, and microorganism) and are absolutely essential as catalysts in biochemical reactions. •Almost every reaction in a cell requires the presence of a specific enzyme– related to its particular protein structure. •A major function of enzymes in a living system is to catalyze the making and breaking of chemical bonds. •Therefore, like any other catalysts, they increase the rate of reaction without themselves undergoing permanent chemical changes. 12/23/2018 Bioreaction engineering. 87
http://buihongquan.com  Over 2000 enzymes have been identified  Often named by adding the - ‘ase’ to the name of substrate acted upon, or the reaction catalyzed such as urease, alcohol dehydrogenase  The majority of cellular reactions are catalyzed by enzymes 12/23/2018 Bioreaction engineering. 88
http://buihongquan.com Some protein enzyme required a non-protein group for their activity. Non protein group: Cofactors: metal ions, Mg, Zn, Mn, Fe. Coenzyme: complex organic molecule, NAD, FAD, CoA Vitamins Catalyze biochemical reactions breaking, forming and rearranging bonds. Catalytic function – very specific and effective (Specific because of conformational shape) Dictated by the enzyme active site. Some active sites allow for multiple substrates. 12/23/2018 Bioreaction engineering. 89
http://buihongquan.com  Enzymes are catalysts  Catalyst: chemical that changes the rate of a reaction without being consumed  Recycled (used multiple times)  Enzymes reduce the activation energy of a reaction  Amount of energy that must be added to get a reaction to proceed 12/23/2018 Bioreaction engineering. 90
http://buihongquan.com Catalysts  A catalyst is unaltered during the course of a reaction and functions in both the forward and reverse directions. In a chemical reaction, a catalyst increases the rate at which the reaction reaches equilibrium.  For a reaction to proceed from starting material to product, the chemical transformations of bond-making and bond-breaking require a minimal threshold amount of energy, termed activation energy.  Generally, a catalyst serves to lower the activation energy of a particular reaction. 12/23/2018 Bioreaction engineering. 91
http://buihongquan.com Enzyme Function Enzymes lower the activation energy of reaction catalyzed ( They do this by binding to the substrate of the reaction, and forming an enzyme-substrate (ES) complex) Substrate binds to a specific site on the enzyme called the active site Multi-substrate reactions possible  ‘Lock and key’ model 12/23/2018 Bioreaction engineering. 92
http://buihongquan.com The activation energy for the decomposition of hydrogen peroxide varies depending on the type of catalysis. Type of Activation catalysis energy Uncatalyzed 18 reaction at kcal/mol 20°C Enzymatically 7 kcal/mol catalyzed (catalase) Chemically 13 catalysed (by kcal/mol Enzyme lower the activation energy of the collodial reaction by binding the substrate and forming an platinum) enzymes enzymes-substrate complex. 12/23/2018 Bioreaction engineering. 93
http://buihongquan.com Comparison of activation energies in the uncatalyzed and catalyzed decompositions of ozone. 12/23/2018 Bioreaction engineering. 94
http://buihongquan.com Important Terms To Remember! • active site - a region of an enzyme comprised of different amino acids where catalysis occurs or a small portion of the surface of an enzyme which a specific chemical reaction is catalyzed • substrate - the molecule being utilized and/or modified by a particular enzyme at its active site • co-factor - organic or inorganic molecules that are required by some enzymes for activity. These include Mg2+, Fe2+, Zn2+ and larger molecules termed co-enzymes like nicotinamide adenine dinucleotide (NAD+), coenzyme A, and many vitamins. 12/23/2018 Bioreaction engineering. 95
http://buihongquan.com Types of Enzymes • holoenzyme - a complete, catalytically active enzyme including all co-factors OR an enzyme containing a non protein group • apoenzyme - the protein portion of a holoenzyme minus the co-factors OR the protein part of holoenzyme • (holoenzyme = apoenzyme+cofactor) • isozyme - (or iso-enzyme) an enzyme that performs the same or similar function of another enzyme that occur in several different molecular forms. 12/23/2018 Bioreaction engineering. 96
http://buihongquan.com Nomenclature of enzyme Originally enzymes were given non descriptive names such as: rennin : curding of milk to start cheese-making cheese processor pepsin : hydrolyzes proteins at acidic pH trypsin : hydrolyzes proteins at mild alkaline pH The nomenclature was later improved by adding the suffix -ase to the name of the substrate with which the enzyme functions, or to the reaction that is catalyzed, for example: 12/23/2018 Bioreaction engineering. 97
http://buihongquan.com Alcohol dehydrogenase Glucose isomerase Glucose oxidase Lactic acid dehydrogenase 12/23/2018 Bioreaction engineering. 98
http://buihongquan.com Enzyme reactions are different from chemical reactions, as follows: 1. An enzyme catalyst is highly specific, and catalyzes only one or a small number of chemical reactions. A great variety of enzymes exist, which can catalyze a very wide range of reactions. 2. The rate of an enzyme-catalyzed reaction is usually much faster than that of the same reaction when directed by nonbiological catalysts at mild reaction condition. 3. A small amount of enzyme is required to produce a desired effect. 4. Enzymes are comparatively sensitive or unstable molecules and require care in their use. 12/23/2018 Bioreaction engineering. 99

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