生物化学之酶化学

生物化学之酶化学的思维导图，内容 酶的组成与功能Components and functions of Enzymes 酶促反应的特点和机制Characteristics and Mechanism of Enzyme Catalyzed Reactions 酶动力学Kinetics of Enzyme Catalyzed Reactions，一起来看。

酶的化学Enzyme

• 酶的组成与功能Components and functions of Enzymes
  • 活性中心 Active Center
    • 必需基团在空间结构上彼此靠近，组成具有特定空间结构的区域，能与底物特异结合并将底物转化为产物。 Some functionalc groups are close enough to form a portion called the active center
  • 必需基团essential group
    • 定义
      • 酶分子中氨基酸残基侧链的化学基团中，一些与酶活性密切相关的基团。
    • 分类
      • 活性中心内
        • 结合基团Binding group
          • to associate with the reactants to form an enzyme-substrate complex
        • 催化基团Catalytic group
          • to catalyze the reactions and convert substrates into products
      • 活性中心外
  • 分子组成Molecular components
    • 单纯酶Simple enzymes
      • consists of only one peptide chain
    • 结合酶Conjugated enzymes
      • • 酶蛋白
          • 决定酶的特异性
        • 辅助因子
          • 决定酶的性质，类型
            • 根据化学本质
              • 金属离子
              • 小分子有机物
            • 根据与酶蛋白结合牢固程度
              • 辅酶Coenzymes
                • 非共价键连接 non-to apoenzymecovalent interactions
              • 辅基Prosthetic groups
                • 共价键连接covalent interactiotions
  • 同工酶Isoenzyme
    • 定义
      • A group of enzymes that catalyze the same reaction but differ from each other in their structure, substrate affinity, Vmax , and regulatory properties.
• 酶促反应的特点和机制Characteristics and Mechanism of Enzyme Catalyzed Reactions
  • 特点
    • 高效性 极高的催化效率 Enzyme-catalyzed reactions have very high catalytic efficiency.
    • 专一性 高度的专一性 Enzymes have a high degree of specificity for their substrates
      • 绝对专一性Absolute specificity
        • Enzymes can recognize only one type of substrate and implement their catalytic functions
      • 相对专一性Relative specificity
        • Enzymes catalyze one class of substrates or one kind of chemical bond in the same type
      • 立体专一性Stereospecificity
        • The enzyme can act on only one form of isomers of the substrates
    • 可调节性 Enzymatic activities are highly regulated in response to the external changes
    • 反应条件温和 The instability of the enzyme
  • 反应机制
    • • 降低活化能
      • • Lock-and-key model（锁钥模型）
          • 绝对专一性
        • Induced-fit model（诱导契合模型）
          • 相对专一性
• 酶动力学Kinetics of Enzyme Catalyzed Reactions
  • 影响因素
    • 酶浓度Enzyme concentration
      • 当[S]＞＞[E]，反应速度与酶浓度成正比。
    • 底物浓度Substrate concentration
      • • • ①[S]较低时,v与[S]呈正比 , 即呈直线关系
          • ②当[S]增加至一定程度时 , v随[S]增加而提高，但不呈直线关系
          • ③ [S]再增加，v达到Vmax
      • Km的意义
        • Km值等于酶促反应速度为最大反应速度一半时的底物浓度，单位是mol/L。 the substrate concentration at which enzyme-catalyzed reaction proceeds at one-half of its maximum velocity
        • Km值是酶的特征性常数 Km is a characteristic constant（特征常数） of E
          • Km值与酶的结构、底物的类别和反应环境（温度、pH、离子强度）有关，与酶的浓度无关。
        • Km值可以表示酶与底物的亲和力
          • 反比
        • 可根据Km值判断代谢途径的关键酶、酶的最适底物
      • Vmax的意义
        • 与酶浓度成正比 It is proportional（成正比）to [E]
    • 温度Temperature
      • • Optimal temperature (最适温度) is the characteristic T at which an enzyme has the maximal catalytic power.
    • pH值
      • • Optimal pH（最适pH）is the characteristic pH at which the enzyme has the maximal catalytic power
    • 抑制剂Inhibitors
      • 不可逆性抑制剂Irreversible inhibition
        • Inhibitors cannot be removed with simple dialysis（透析）or super￾ filtration（超滤）.
        • 共价键
        • 结合位置：活性中心内的必需基团
        • Inhibitors are covalently（共价的）bound to the essential groups of enzymes.
      • 可逆性抑制剂Reversible inhibition
        • Inhibitors are bound to enzymes non- covalently（非共价的） 与酶或酶—底物复合物结合
        • 竞争性抑制剂Competitive inhibition
          • • I与S结构类似，竞争酶的活性中心；
              • Competitive inhibitors share the structural similarities with that of substrates. Competitive inhibitors compete for the active sites with
            • 抑制程度取决于抑制剂与酶的相对亲和力及浓度比；
              • Inhibition depends on the affinity of enzymes and the ratio of [E] to [S].
            • 动力学特点：Vmax不变，表观Km↑
        • 反竞争性抑制剂Uncompetitive inhibition
          • • 抑制剂只与ES结合；
              • Uncompetitive inhibitors bind only to the enzyme-substrate complexes
            • 结合部位在活性中心外；
            • 动力学特点： Vmax↓，表观 Km↓。
        • 非竞争性抑制剂Non-competitive inhibition
          • • 抑制剂与酶活性中心外的必需基团结合；
              • Inhibitors bind to other sites rather than the active sites on the free enzymes or the E-S complexes
            • 不影响底物与活性中心的结合；
              • The E-I complex formation does not affect the binding of substrates.
            • 动力学特点：Vmax↓，表观Km不变。
• 酶催化剂它有特殊的特性来促进生物系统中的生化反应。 酶催化反应通常在温和的条件下进行。 Enzymes catalystsa that have special characteristics to facilitate the biochemical reactions in the biological systems. Enzyme-catalyzed reactions take place usually relativeulnyd er mild 。

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酶的化学Enzyme

• 酶的组成与功能Components and functions of Enzymes
  • 活性中心 Active Center
    • 必需基团在空间结构上彼此靠近，组成具有特定空间结构的区域，能与底物特异结合并将底物转化为产物。 Some functionalc groups are close enough to form a portion called the active center
  • 必需基团essential group
    • 定义
      • 酶分子中氨基酸残基侧链的化学基团中，一些与酶活性密切相关的基团。
    • 分类
      • 活性中心内
        • 结合基团Binding group
          • to associate with the reactants to form an enzyme-substrate complex
        • 催化基团Catalytic group
          • to catalyze the reactions and convert substrates into products
      • 活性中心外
  • 分子组成Molecular components
    • 单纯酶Simple enzymes
      • consists of only one peptide chain
    • 结合酶Conjugated enzymes
      • • 酶蛋白
          • 决定酶的特异性
        • 辅助因子
          • 决定酶的性质，类型
            • 根据化学本质
              • 金属离子
              • 小分子有机物
            • 根据与酶蛋白结合牢固程度
              • 辅酶Coenzymes
                • 非共价键连接 non-to apoenzymecovalent interactions
              • 辅基Prosthetic groups
                • 共价键连接covalent interactiotions
  • 同工酶Isoenzyme
    • 定义
      • A group of enzymes that catalyze the same reaction but differ from each other in their structure, substrate affinity, Vmax , and regulatory properties.
• 酶促反应的特点和机制Characteristics and Mechanism of Enzyme Catalyzed Reactions
  • 特点
    • 高效性 极高的催化效率 Enzyme-catalyzed reactions have very high catalytic efficiency.
    • 专一性 高度的专一性 Enzymes have a high degree of specificity for their substrates
      • 绝对专一性Absolute specificity
        • Enzymes can recognize only one type of substrate and implement their catalytic functions
      • 相对专一性Relative specificity
        • Enzymes catalyze one class of substrates or one kind of chemical bond in the same type
      • 立体专一性Stereospecificity
        • The enzyme can act on only one form of isomers of the substrates
    • 可调节性 Enzymatic activities are highly regulated in response to the external changes
    • 反应条件温和 The instability of the enzyme
  • 反应机制
    • • 降低活化能
      • • Lock-and-key model（锁钥模型）
          • 绝对专一性
        • Induced-fit model（诱导契合模型）
          • 相对专一性
• 酶动力学Kinetics of Enzyme Catalyzed Reactions
  • 影响因素
    • 酶浓度Enzyme concentration
      • 当[S]＞＞[E]，反应速度与酶浓度成正比。
    • 底物浓度Substrate concentration
      • • • ①[S]较低时,v与[S]呈正比 , 即呈直线关系
          • ②当[S]增加至一定程度时 , v随[S]增加而提高，但不呈直线关系
          • ③ [S]再增加，v达到Vmax
      • Km的意义
        • Km值等于酶促反应速度为最大反应速度一半时的底物浓度，单位是mol/L。 the substrate concentration at which enzyme-catalyzed reaction proceeds at one-half of its maximum velocity
        • Km值是酶的特征性常数 Km is a characteristic constant（特征常数） of E
          • Km值与酶的结构、底物的类别和反应环境（温度、pH、离子强度）有关，与酶的浓度无关。
        • Km值可以表示酶与底物的亲和力
          • 反比
        • 可根据Km值判断代谢途径的关键酶、酶的最适底物
      • Vmax的意义
        • 与酶浓度成正比 It is proportional（成正比）to [E]
    • 温度Temperature
      • • Optimal temperature (最适温度) is the characteristic T at which an enzyme has the maximal catalytic power.
    • pH值
      • • Optimal pH（最适pH）is the characteristic pH at which the enzyme has the maximal catalytic power
    • 抑制剂Inhibitors
      • 不可逆性抑制剂Irreversible inhibition
        • Inhibitors cannot be removed with simple dialysis（透析）or super￾ filtration（超滤）.
        • 共价键
        • 结合位置：活性中心内的必需基团
        • Inhibitors are covalently（共价的）bound to the essential groups of enzymes.
      • 可逆性抑制剂Reversible inhibition
        • Inhibitors are bound to enzymes non- covalently（非共价的） 与酶或酶—底物复合物结合
        • 竞争性抑制剂Competitive inhibition
          • • I与S结构类似，竞争酶的活性中心；
              • Competitive inhibitors share the structural similarities with that of substrates. Competitive inhibitors compete for the active sites with
            • 抑制程度取决于抑制剂与酶的相对亲和力及浓度比；
              • Inhibition depends on the affinity of enzymes and the ratio of [E] to [S].
            • 动力学特点：Vmax不变，表观Km↑
        • 反竞争性抑制剂Uncompetitive inhibition
          • • 抑制剂只与ES结合；
              • Uncompetitive inhibitors bind only to the enzyme-substrate complexes
            • 结合部位在活性中心外；
            • 动力学特点： Vmax↓，表观 Km↓。
        • 非竞争性抑制剂Non-competitive inhibition
          • • 抑制剂与酶活性中心外的必需基团结合；
              • Inhibitors bind to other sites rather than the active sites on the free enzymes or the E-S complexes
            • 不影响底物与活性中心的结合；
              • The E-I complex formation does not affect the binding of substrates.
            • 动力学特点：Vmax↓，表观Km不变。
• 酶催化剂它有特殊的特性来促进生物系统中的生化反应。 酶催化反应通常在温和的条件下进行。 Enzymes catalystsa that have special characteristics to facilitate the biochemical reactions in the biological systems. Enzyme-catalyzed reactions take place usually relativeulnyd er mild 。

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