Enzyme
第
一
节
酶
的
概
念
及
特
点
An Introduction to
Enzymes
Much of the history of biochemistry is the history
of enzyme research,Biological catalysis was first
recognized and described in the late 1700s,in studies
on the digestion of meat by secretions of the stomach,
and research continued in the 1800s with examinations
of the conversion of starch to sugar by saliva and
various plant extracts,In the 1850s,Louis Pasteur
concluded that fermentation of sugar into alcohol by
yeast is catalyzed by,ferments.”
一,酶的概念
An Introduction to
Enzymes
He postulated that these ferments were inseparable
from the structure of living yeast cells; this view,called
vitalism(活力论 ),prevailed for decades,Then in 1897
Eduard Buchner discovered that yeast extracts could
ferment sugar to alcohol,proving that fermentation was
promoted by molecules that continued to function when
removed from cells,Frederick W,Kühne called these
molecules enzymes,As vitalistic notions of life were
disproved,the isolation of new enzymes and the
investigation of their properties advanced the science of
biochemistry.
An Introduction to
Enzymes
The isolation and crystallization of urease by
James Sumner in 1926 provided a breakthrough in
early enzyme studies,Sumner found that urease
crystals consisted entirely of protein,and he
postulated that all enzymes are proteins,In the
absence of other examples,this idea remained
controversial for some time,Only in the 1930s was
Sumner’s conclusion widely accepted,after John
Northrop and Moses Kunitz crystallized pepsin,
trypsin,and other digestive enzymes and found
them also to be proteins.
An Introduction to
Enzymes
During this period,J,B,S,Haldane wrote a
treatise entitled Enzymes,Although the molecular
nature of enzymes was not yet fully appreciated,
Haldane made the remarkable suggestion that
weak bonding interactions between an enzyme and
its substrate might be used to catalyze a reaction.
This insight lies at the heart of our current
understanding of enzymatic catalysis.
一,酶的概念
With the exception of a small group of
catalytic RNA molecules,all enzymes are
proteins,Their catalytic activity depends on the
integrity of their native protein conformation,If an
enzyme is denatured or dissociated into its
subunits,catalytic activity is usually lost,If an
enzyme is broken down into its component amino
acids,its catalytic activity is always destroyed.
Thus the primary,secondary,tertiary,and
quaternary structures of protein enzymes are
essential to their catalytic activity.
Most Enzymes Are Proteins
一,酶的概念
生物体内的反应是在很 温和 的条件（如温和
的温度、接近中性的 pH）下进行的，而同样的反
应若在非生物条件下进行，则需要高温、高压、
强酸、强碱等剧烈的条件 。
酶的概念 —酶是由生物细胞产生的以蛋白质
为主要成分的生物催化剂。
The sweet taste of freshly picked corn (maize) is
due to the high level of sugar in the kernels,Store-
bought corn (several days after picking) is not as
sweet,because about 50% of the free sugar is
converted to starch within one day of picking,To
preserve the sweetness of fresh corn,the husked
ears can be immersed in boiling water for a few
minutes (“blanched”) then cooled in cold water,Corn
processed in this way and stored in a freezer
maintains its sweetness,What is the biochemical
basis for this procedure?
question?-- Keeping the Sweet Taste of Corn
一,酶的概念
酶是 但酶发挥其催化作用并不局限于活细胞内，在许
多情况下，细胞内产生的酶需分泌到细胞外或转移到
其它组织器官中发挥作用，如胰蛋白酶、脂酶、淀粉
酶等水解酶。 把由细胞内产生并在细胞内发挥作用的
酶称为胞内酶,而将细胞内产生后分泌细胞外起作用
的酶叫胞外酶。
一,酶的概念
在本章节中把酶所催化的反应称作酶促反应
，发生化学反应前的物质称底物 （ substrate）,
而反应后生成的物质称产物（ product）。
二,酶的特性
1,酶具有共同于一般催化剂的特征
? 用量少 ;
? 只能催化热力学上允许的反应 ;
? 不改变反应的平衡点，而只能缩短时
间。催化机理都是降低反应所需的活
化能。
酶促反应 的速度比 非酶促反应 通常要快
105~1017 倍
如此高的催化效率使生物体内含量
甚微的酶能催化大量的物质转化 。
二,酶的特性
2,酶不共同于一般催化剂的特征
? 催化效率极高
用简单的实验证明酶的催化效率：
铁屑 肝糜 肝糜 (煮 )
2 H2O2 2 H2O + O2
二,酶的特性
1000 109
二,酶的特性
二,酶的特性
2,酶不共同于一般催化剂的特征
铂：催化许多反应，包括有机反应
H+：淀粉、脂肪、蛋白质、蔗糖等
酶：只作用于结构近似的分子，甚至
只催化一种化合物。
? 专一性很强
二,酶的特性
2,酶不共同于一般催化剂的特征
? 酶对环境条件极为敏感
? 酶活性可以调控
酶催化的专一性 (specificity)是指酶对它所催
化的反应及其底物具有的严格的选择性 。 通常一种酶
只能催化一种或一类化学反应 。
由酶对底物选择的严格程度, 可将酶的专一性分为多
种类型：
三,酶的专一性的类型
1,绝对专业性 —除一种底物外，酶都不能催化其它
反应的特性
三,酶的专一性及其类型
H 2 N N H 2C
O
2 N H 3 + C O 2
脲 酶
H 2 O
2 相对专一性 —酶能催化在结构上类似的一系列化合物
反应特怔 。
A 基团专一性 (group specificity)—在催化 A-B化合
物中, 酶对其中的一个基团具有高度甚至是绝对专一
性, 而对另一个基团则具有相对专一性的特性 。
O
C H 2 O H
O H
OH
O H
O R
? 葡 萄 糖 苷
三,酶的专一性及其类型
2 相对专一性 —酶能催化在结构上类似的一系列化合物
反应特怔 。
B 键专一性 (bond specificity)—在催化 A-B化合物
中, 酶对 A,B基团的结构要求不严, 而要求有一定的
化学键便能进行催化反应特性 。
三,酶的专一性及其类型
C 立体专一性 (stereo specificity)—一种酶只能对
一种立体异构体起催化作用, 对其对映体则全无作用
的特性 。 a.立体异构专一性,
L 氨 基 酸 ? 酮 酸 + N H 3 + H 2 O 2
L 氨 基 酸 氧 化 酶
H 2 O + O 2
三,酶的专一性及其类型
C 立体专一性 (stereo specificity)—一种酶只能对
一种立体异构体起催化作用, 对其对映体则全无作用
的特性 。 B.几何异构专一性,
H O O C C H
H C C O O H
延 胡 索 酸
延 胡 索 酸 酶
C H 2 C O O H
C H C O O HH O
苹 果 酸
三,酶的专一性及其类型
Summry
绝对专一性 一种酶只能催化一种底物。如 6-磷酸葡萄糖磷酸酯酶。
立体专一性 一种酶只能对一种立体异构体起催化作用。
相对专一性
键专一性
一种酶只作用于一定的化学
键，对键两侧的基团无要求
。如酯酶。
基团
专一性
不仅要求底物具有一定的化
学键，还对键某一侧的基团
有选择性。如磷酸单酯酶。
三,酶的专一性及其类型
第
一
节
酶
的
概
念
及
特
点
An Introduction to
Enzymes
Much of the history of biochemistry is the history
of enzyme research,Biological catalysis was first
recognized and described in the late 1700s,in studies
on the digestion of meat by secretions of the stomach,
and research continued in the 1800s with examinations
of the conversion of starch to sugar by saliva and
various plant extracts,In the 1850s,Louis Pasteur
concluded that fermentation of sugar into alcohol by
yeast is catalyzed by,ferments.”
一,酶的概念
An Introduction to
Enzymes
He postulated that these ferments were inseparable
from the structure of living yeast cells; this view,called
vitalism(活力论 ),prevailed for decades,Then in 1897
Eduard Buchner discovered that yeast extracts could
ferment sugar to alcohol,proving that fermentation was
promoted by molecules that continued to function when
removed from cells,Frederick W,Kühne called these
molecules enzymes,As vitalistic notions of life were
disproved,the isolation of new enzymes and the
investigation of their properties advanced the science of
biochemistry.
An Introduction to
Enzymes
The isolation and crystallization of urease by
James Sumner in 1926 provided a breakthrough in
early enzyme studies,Sumner found that urease
crystals consisted entirely of protein,and he
postulated that all enzymes are proteins,In the
absence of other examples,this idea remained
controversial for some time,Only in the 1930s was
Sumner’s conclusion widely accepted,after John
Northrop and Moses Kunitz crystallized pepsin,
trypsin,and other digestive enzymes and found
them also to be proteins.
An Introduction to
Enzymes
During this period,J,B,S,Haldane wrote a
treatise entitled Enzymes,Although the molecular
nature of enzymes was not yet fully appreciated,
Haldane made the remarkable suggestion that
weak bonding interactions between an enzyme and
its substrate might be used to catalyze a reaction.
This insight lies at the heart of our current
understanding of enzymatic catalysis.
一,酶的概念
With the exception of a small group of
catalytic RNA molecules,all enzymes are
proteins,Their catalytic activity depends on the
integrity of their native protein conformation,If an
enzyme is denatured or dissociated into its
subunits,catalytic activity is usually lost,If an
enzyme is broken down into its component amino
acids,its catalytic activity is always destroyed.
Thus the primary,secondary,tertiary,and
quaternary structures of protein enzymes are
essential to their catalytic activity.
Most Enzymes Are Proteins
一,酶的概念
生物体内的反应是在很 温和 的条件（如温和
的温度、接近中性的 pH）下进行的，而同样的反
应若在非生物条件下进行，则需要高温、高压、
强酸、强碱等剧烈的条件 。
酶的概念 —酶是由生物细胞产生的以蛋白质
为主要成分的生物催化剂。
The sweet taste of freshly picked corn (maize) is
due to the high level of sugar in the kernels,Store-
bought corn (several days after picking) is not as
sweet,because about 50% of the free sugar is
converted to starch within one day of picking,To
preserve the sweetness of fresh corn,the husked
ears can be immersed in boiling water for a few
minutes (“blanched”) then cooled in cold water,Corn
processed in this way and stored in a freezer
maintains its sweetness,What is the biochemical
basis for this procedure?
question?-- Keeping the Sweet Taste of Corn
一,酶的概念
酶是 但酶发挥其催化作用并不局限于活细胞内，在许
多情况下，细胞内产生的酶需分泌到细胞外或转移到
其它组织器官中发挥作用，如胰蛋白酶、脂酶、淀粉
酶等水解酶。 把由细胞内产生并在细胞内发挥作用的
酶称为胞内酶,而将细胞内产生后分泌细胞外起作用
的酶叫胞外酶。
一,酶的概念
在本章节中把酶所催化的反应称作酶促反应
，发生化学反应前的物质称底物 （ substrate）,
而反应后生成的物质称产物（ product）。
二,酶的特性
1,酶具有共同于一般催化剂的特征
? 用量少 ;
? 只能催化热力学上允许的反应 ;
? 不改变反应的平衡点，而只能缩短时
间。催化机理都是降低反应所需的活
化能。
酶促反应 的速度比 非酶促反应 通常要快
105~1017 倍
如此高的催化效率使生物体内含量
甚微的酶能催化大量的物质转化 。
二,酶的特性
2,酶不共同于一般催化剂的特征
? 催化效率极高
用简单的实验证明酶的催化效率：
铁屑 肝糜 肝糜 (煮 )
2 H2O2 2 H2O + O2
二,酶的特性
1000 109
二,酶的特性
二,酶的特性
2,酶不共同于一般催化剂的特征
铂：催化许多反应，包括有机反应
H+：淀粉、脂肪、蛋白质、蔗糖等
酶：只作用于结构近似的分子，甚至
只催化一种化合物。
? 专一性很强
二,酶的特性
2,酶不共同于一般催化剂的特征
? 酶对环境条件极为敏感
? 酶活性可以调控
酶催化的专一性 (specificity)是指酶对它所催
化的反应及其底物具有的严格的选择性 。 通常一种酶
只能催化一种或一类化学反应 。
由酶对底物选择的严格程度, 可将酶的专一性分为多
种类型：
三,酶的专一性的类型
1,绝对专业性 —除一种底物外，酶都不能催化其它
反应的特性
三,酶的专一性及其类型
H 2 N N H 2C
O
2 N H 3 + C O 2
脲 酶
H 2 O
2 相对专一性 —酶能催化在结构上类似的一系列化合物
反应特怔 。
A 基团专一性 (group specificity)—在催化 A-B化合
物中, 酶对其中的一个基团具有高度甚至是绝对专一
性, 而对另一个基团则具有相对专一性的特性 。
O
C H 2 O H
O H
OH
O H
O R
? 葡 萄 糖 苷
三,酶的专一性及其类型
2 相对专一性 —酶能催化在结构上类似的一系列化合物
反应特怔 。
B 键专一性 (bond specificity)—在催化 A-B化合物
中, 酶对 A,B基团的结构要求不严, 而要求有一定的
化学键便能进行催化反应特性 。
三,酶的专一性及其类型
C 立体专一性 (stereo specificity)—一种酶只能对
一种立体异构体起催化作用, 对其对映体则全无作用
的特性 。 a.立体异构专一性,
L 氨 基 酸 ? 酮 酸 + N H 3 + H 2 O 2
L 氨 基 酸 氧 化 酶
H 2 O + O 2
三,酶的专一性及其类型
C 立体专一性 (stereo specificity)—一种酶只能对
一种立体异构体起催化作用, 对其对映体则全无作用
的特性 。 B.几何异构专一性,
H O O C C H
H C C O O H
延 胡 索 酸
延 胡 索 酸 酶
C H 2 C O O H
C H C O O HH O
苹 果 酸
三,酶的专一性及其类型
Summry
绝对专一性 一种酶只能催化一种底物。如 6-磷酸葡萄糖磷酸酯酶。
立体专一性 一种酶只能对一种立体异构体起催化作用。
相对专一性
键专一性
一种酶只作用于一定的化学
键，对键两侧的基团无要求
。如酯酶。
基团
专一性
不仅要求底物具有一定的化
学键，还对键某一侧的基团
有选择性。如磷酸单酯酶。
三,酶的专一性及其类型
