(三)国际系统分类法及酶的编号 国际酶学委员会,根据各种酶所催化反应的类型, 把酶分为6大类,即氧化还原酶类、转移酶类、水解 酶类、裂合酶类、异构酶类和连接酶类。分别用1、2 3、4、5、6来表示。再根据底物中被作用的基团或 键的特点将每一大类分为若干个亚类,每一个亚类又 按顺序编成1、2、3、4.等数字。每一个亚类可 再分为亚亚类,仍用1、2、3、4.…编号。每一个 酶的分类编号由4个数字组成,数字间由“·隔开, 编 号之前冠以EC( Enzyme Commision)
（三）国际系统分类法及酶的编号 国际酶学委员会，根据各种酶所催化反应的类型， 把酶分为6大类，即氧化还原酶类、转移酶类、水解 酶类、裂合酶类、异构酶类和连接酶类。分别用1、2、 3、4、5、6来表示。再根据底物中被作用的基团或 键的特点将每一大类分为若干个亚类，每一个亚类又 按顺序编成1、2、3、4……等数字。每一个亚类可 再分为亚亚类，仍用1、2、3、4……编号。每一个 酶的分类编号由4个数字组成，数字间由“·”隔开， 编 号之前冠以EC（Enzyme Commision)
1.氧化还原酶类( Oxidoreductases): Any enzyme which catalyzes a reduction has to also catalyze the reverse (oxidation) reaction, thus the double-barreled name"oxidoreductase. 2.转移酶类( Transferases): a common example involves transfer of a phosphate between atp and a sugar molecule 3.水解酶类( Hydrolases): The hydrolysis of an ester would be an example of such a reaction 4.裂合酶类( Lyases): Reactions which add a small molecule such as water or ammonia to a double bond(and the reverse, elimination, reactions)are catalyzed by lyases. 5.异构酶类( Isomerases): These enzymes catalyze the conversion of a molecule into an isomer. The cis-trans interconversion of maleate and fumarate is an example 6.连接酶类( Ligases): These enzymes catalyze reactions which make bonds to join together (ligate) smaller molecules to make larger ones
1. 氧化还原酶类（Oxidoreductases）： Any enzyme which catalyzes a reduction has to also catalyze the reverse (oxidation) reaction, thus the double-barreled name "oxidoreductase." 2. 转移酶类（Transferases）: A common example involves transfer of a phosphate between ATP and a sugar molecule. 3. 水解酶类（Hydrolases）: The hydrolysis of an ester would be an example of such a reaction. 4. 裂合酶类（Lyases）: Reactions which add a small molecule such as water or ammonia to a double bond (and the reverse, elimination, reactions) are catalyzed by lyases. 5. 异构酶类（Isomerases）: These enzymes catalyze the conversion of a molecule into an isomer. The cis-trans interconversion of maleate and fumarate is an example. 6. 连接酶类（Ligases）: These enzymes catalyze reactions which make bonds to join together (ligate) smaller molecules to make larger ones
table 8-3 International classification of enzymes* No Class Type of reaction catalyzed Oxidoreductases Transfer of electrons(hydride ions or H atoms Transferases Group-transfer reactions 123456 Hydrolases Hydrolysis reactions(transfer of functional groups to water Lyases Addition of groups to double bonds, or formation of double bonds by removal of groups Isomerases Transfer of groups within molecules to yield isomeric forms Ligases Formation of c-C C-S c-0 and C-N bonds by condensation reactions coupled to ATP cleavage Most enzymes catalyze the transfer of electrons, atoms, or functional groups. They are therefore classified, given code numbers, and assigned names according to the type of transfer reaction, the group donor, and the group acceptor
Classification of enzymes Based on type of reaction Oxidoreductase catalyze a redox reaction Transferase transfer a functional group Hydrolase cause hydrolysis reactions Lyase break C-o.C-C or C-N bonds Isomerases rearrange functional groups Ligase join two molecules
(小胖辑 hydrolase ■水解酶催化底物的加水分解反应。 ■主要包括淀粉酶、蛋白酶、核酸酶及脂酶等。 例如,脂肪酶( Lipase)催化的脂的水解反应: HO R-COOCH2CH3 RCooh +CHrCHOH
◼ 水解酶催化底物的加水分解反应。 ◼ 主要包括淀粉酶、蛋白酶、核酸酶及脂酶等。 ◼ 例如，脂肪酶(Lipase)催化的脂的水解反应： (1) 水解酶 hydrolase H2O R COOCH2 CH3 RCOOH CH3 CH2OH