上降充通大学 SHANGHAI JIAO TONG UNIVERSITY Chapter 8: Enzymes:Basic Concepts and Kinetics 酶：基本概念及动力学 Berg·Tymoczko·Stryer Biochemistry Sixth Edition
Berg • Tymoczko • Stryer Biochemistry Sixth Edition Chapter 8: Enzymes: Basic Concepts and Kinetics 酶：基本概念及动力学
OUTLINES 1.Enzymes Are Powerful and Highly Specific Catalysts一概论 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一化学 4.The Michaelis-Menten Model Accounts for the Kinetic Properties of Many Enzymes-动力学 5.Enzymes Can Be Inhibited by Specific Molecules一抑制作用
1. Enzymes Are Powerful and Highly Specific Catalysts － 概论 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 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
E+ESE+P V。=k2[ES] Rate of formation of ES=kES] (15) Rate of breakdown of ES =(k_1+k2)ES (16) George Briggs and John Haldane suggested the steadystate assumption in 1924. 稳态假说：酶一底物复合物形成及分解的速度相同 k1E S=(k-1+k2)ES
George Briggs and John Haldane suggested the steadystate assumption in 1924. 稳态假说：酶－底物复合物形成及分解的速度相同 Vo=k2［ES］
Michaelis-Menten kinetics max Vmax Vo Vmax IS KM When [S]KM, Vmax/2 Vo Vmax/2. KM Substrate concentration [S]- The maximal velocity (Vmax)is approached asymptotically 最大速度Vmax是个渐进的最大速度。 The Michaelis constant(KM)is the substrate concentration yielding a velocity of Vmax/2. 米氏常数Km为最大速度一半时的底物浓度
Michaelis-Menten kinetics The maximal velocity (Vmax) is approached asymptotically 最大速度Vmax是个渐进的最大速度。 The Michaelis constant (KM) is the substrate concentration yielding a velocity of Vmax/ 2. 米氏常数Km 为最大速度一半时的底物浓度。 When [S] = KM, Vo = Vmax/2
The physiological consequence of KM:Km生理学意义 The sensitivity of some persons to ethanol..酒精敏感人群 Alcohol dehydrogenane Liver CHCH2OH NAD CH CHO H+NADH the cause of the symptoms CH2CHO is processed to acetate by aldehyde dehydrogenase 乙醛能为7醛脱氢醢降解。 Aldehyde dehydrogenase CH;CHO NAD*+H2O= CH COO-NADH +2 H+ Two forms of the aldehyde dehydrogenase:两套酶系统 一a low KM mitochondrial form较低底物浓度就可以启动反应 -a high KM cytoplasmic form. In susceptible persons,the mitochondrial enzyme is less active owing to the substitution of a single amino acid
The sensitivity of some persons to ethanol. 酒精敏感人群 Liver CH3CHO is processed to acetate by aldehyde dehydrogenase. 乙醛能为乙醛脱氢酶降解。 Two forms of the aldehyde dehydrogenase：两套酶系统 － a low KM mitochondrial form 较低底物浓度就可以启动反应 － a high KM cytoplasmic form. The physiological consequence of KM: Km生理学意义 In susceptible persons, the mitochondrial enzyme is less active owing to the substitution of a single amino acid. the cause of the symptoms