CH6-Gangan生化课件-酶.ppt

酶 --- Enzyme Zhangguangxian Ph.D zhangguangxian@gzhtcm.edu.cn QQ:Tel教学大纲目的要求 掌握酶化学本质、组成及酶促反应特点 熟悉酶促反应动力学 了解酶的催化机制、命名、分类以及与医学的关系 Structure of Enzyme Definition of Enzyme 酶：由活细胞具有催化活性的蛋白质 分类： 生物催化剂：蛋白质(酶)和核酸 酶分子组成：单纯酶和结合酶 化学本质：蛋白质 具有蛋白质所有的理化性质和生物学特征 Components of Enzyme Some terms should be noticed Holoenzyme Apoenzyme and cofactor Cofactor：Ions; coenzyme/prosthetic group Active center binding group and catalytic group Characteristics of enzymatic reaction Instability (protein) High efficiency (△G=△ H-T△ S) High specificity Absolute: catalyze one specific substrate/reaction Relative: catalyze one kind of bond/compounds Stereo/optical: “three-point attachment” Regulable (multi-level and multi-mechanism; multiple options are available ) Mechanism of catalytic reaction How do the E-S bind with each other: ‘lock-key’ model ‘induced-fit’ model Factors responsible for high efficiency Proximity and Orientation Transition-state stabilization Some terms Zymogen and activation Zymogen: An inactive precursor of an enzyme. particularly a proteolytic enzyme Activation: zymogen enzyme Isozyme: catalyze the same reaction with different physical properties LDH(1-5): lactate pyruvate LDH1---heart LDH5--- skeletal muscle Kinetics of enzymatic reaction [S] influences the rate of reaction Michaelis-menten equation 稳态：是指ES的生成速度与分解速度相等，即 [ES]恒定。 K1 ([Et]－[ES]) [S]＝K2 [ES] + K3 [ES] [S] influences the rate of reaction The significance of Km Km=[S]v=V/2（mol/L） One enzyme has different Km to different substrate Natural substrate: the lowest Km, the fastest velocity Km is a characteristic constant E, S, Buffer Km reflects the affinity of enzyme to substrate The lower the Km, the greater the affinity Km and Vmax determination The Double-Reciprocal Plot Kinetics of enzymatic reaction [E] influences the rate of reaction Kinetics of enzymatic reaction T influences the rate of reaction Kinetics of enzymatic reaction pH value