酶第8章(1)上海交大生化课件

4. The Michaelis-Menten Model Accounts for the Kinetic Properties of Many Enzymes －动力学
5. Enzymes Can Be Inhibited by Specific Molecules －抑制作用
OUTLINES
are called substrates 底物.
A+B C+D
Substrates
Products
An enzyme usually catalyzes a single chemical
reaction or a set of closely related reactions.
Side reactions 副反应 leading to the wasteful formation of by-products 副产物 are rare in enzyme-catalyzed reactions, in contrast with uncatalyzed ones.
A + B C + D + D’ Substrates Products by-products
Proteolytic enzymes: in vivo体内vs in vitro体外 Proteolytic enzymes 蛋白水解酶 catalyze proteolysis, the hydrolysis of a peptide bond 肽键 in vivo.
determine the patterns of chemical transformations.
Enzymes mediate the transformation of one form of energy into another. 参与能量转化
Catalytic diversity 催化多样性
- trypsin: a proteolytic enzyme secreted by the pancreas. 2. Most enzymes are named for their substrates and for the
reactions that they catalyze, with the suffix "ase" added. - ATPase: an enzyme that breaks down ATP, - ATP synthase: an enzyme that synthesizes ATP.
Proteins as a class of macromolecules are highly effective catalysts for an enormous diversity of chemical reactions because of their capacity to specifically bind a very wide range of molecules. 主要六大类催化反应
4. The Michaelis-Menten Model Accounts for the Kinetic Properties of Many Enzymes －动力学
5. Enzymes Can Be Inhibited by Specific Molecules －抑制作用
Enzymes Are Powerful
By selectively stabilizing a transition state, an enzyme determines which one of several potential chemical reactions actually takes place.
OUTLINES
1. Enzymes Are Powerful and Highly Specific Catalysts － 概论
Proteolytic enzymes differ markedly in their degree of substrate specc enzymes: (A) Trypsin 胰蛋白酶：cleaves on the
carboxyl side of Arg and Lys residues; (B) Thrombin 凝血酶： cleaves ArgGly bonds in particular sequences only. (C) Papain 木瓜蛋白酶：from papaya
Products
The transfer of CO2 from the tissues （组织） into the blood （血液） and then to the alveolar (肺泡的) air would
be less complete in the absence of this enzyme. This catalyzed reaction is 107 times as fast as the uncatalyzed
The most striking characteristics：特点 － Catalytic power （催化高效性） － Specificity （选择性）
Chemical nature: － Proteins 蛋白质 (Nearly all known enzymes are
proteins, but proteins are not an absolute monopoly on catalysis); － Catalytically active RNA molecules : a biocatalyst early in evolution (Section 2.2.2).
2. Free Energy Is a Useful Thermodynamic Function for Understanding Enzymes －热力学
3. Enzymes Accelerate Reactions by Facilitating the Formation of the Transition State －化学
Active site 活性中心
Active site 活性中心： Catalysis takes place at a particular site on the enzyme.
By untilizing the full repertoire of intermolecular forces 分子间作用力, enzymes bring substrates together in an optimal orientation定位, the prelude to making and breaking chemical bonds. They catalyze reactions by stabilizing transition states过渡态, the highest-energy species高能物质 in reaction pathways.
Enzymes accelerate reactions by factors of as much as a million or more.
Indeed, most reactions in biological systems do not take place at perceptible rates in the absence of enzymes.
1. Enzymes Are Powerful and Highly Specific Catalysts
2. Free Energy Is a Useful Thermodynamic Function for Understanding Enzymes －热力学
3. Enzymes Accelerate Reactions by Facilitating the Formation of the Transition State －化学
体 内
Most proteolytic enzymes also catalyze a different but related reaction in vitro namely, the hydrolysis of an ester bond 酯键.
体 外
useful in experimental investigations of these enzymes.
designated 2.7.4. 4. The final number designates the acceptor more precisely. In
regard to NMP kinase, a nucleoside monophosphate is the acceptor, and the enzyme's designation is EC 2.7.4.4.
Chapter 8: Enzymes: Basic Concepts and Kinetics
酶：基本概念及动力学
Berg • Tymoczko • Stryer
Biochemistry Sixth Edition
INTRODUCTION
Enzymes（酶）： The catalysts of biological systems 生物催化剂 They are remarkable molecular devices that
Nomenclature for enzymes：in 1964，Enzyme Commission of the International Union of Biochemistry（国际生化联盟） •Reactions were divided into six major groups. These groups were subdivided and further subdivided, so that a four-digit number preceded by the letters EC for Enzyme Commission could precisely identify all enzymes.