中南大学生物化学考研ch15酶特性和调控

Ser Phe COO-
+ H3N+
Gly Asn Lys Trp COO-
+ H3N+ Glu Val COO-
(c)
Gly Arg
Ala Ser Phe Gly Asn Lys
Gly Arg Ala Ser Phe
Gly Asn Lys Trp
Trp Glu Val Glu Val
Question: Please compare the difference in mechanism
OH
Tyrosine 酪氨酸
Tryptophan 色氨酸
Control of enzyme action
Control of enzyme amount
H3N+ Gly Arg COO- + H3N+ Ala Ser Phe Gly Asn Lys COO+ H3N+ Trp Glu Val COO-
(b) H3N+
Gly Arg Ala Ser Phe Gly Asn Lys Trp Glu Val COOChymotrypsin
H3N+
Gly Arg Ala
Binding of substrate induces a conformational change in the active site of enzyme.
Enzyme may distort the substrate, forcing it into a conformation similar to that of the transition state.
Shape of the substrate and the active site of the enzyme are rigid and fixed, they fit together like a key into its lock
Induced-fit model 诱导-契合模型
Founder: Daniel E., Koshland Jr., 1958 Principle
Control of enzyme action Control of enzyme amount 酶量的控制 Control of enzyme activity 酶活性的控制
Enzyme specificity
Specificity is the result of molecular recognition
COO-
CH (CH2)4 NH3+
Carbamidine
NH2
Lysine 赖氨酸
Trp, Tyr, Phe
O OC
GlySer
COO+H3N C H
CH3 Alanine 丙氨酸 Gly, Ala
VaTl hr
Asp
COONH3+ C H
CH2 COO-
Aspartate 天冬氨酸
COO+H3N C H +H3N
The induced fit model (ex. of hexokinase)
Before glucose binding
After glucose binding
Substrate is highly specific to its enzyme
The specificity between enzyme and its substrate depends on the properties and spatial arrangement of the amino acid residues forming the active site of an enzyme
of specificity among the serine proteases trypsin, chymotrypsin and elastase. 请比较丝氨酸胰蛋白 酶、胰凝乳蛋白酶、弹性蛋白酶在特异性机制的区 别
+H3N
Arginie 精氨酸
COO-
CH (CH2)3
+H3N
NH C NH2+
Elastase弹性蛋白酶(胰肽酶E)：cleaves C-terminal side of small uncharged amino acid residues (Gly, Ala)
(a) H3N+
Gly Arg Ala Ser Phe Gly Asn Lys Trp Glu Val COOTrypsin
Biochemistry
For Speciality of Biotechnology or Bioengineering at CSU Mr. XIA Jinlan
Contents
Enzyme specificity (self-study) 酶的特异 性(自学) The “lock and key” hypothesis 锁钥假设 The “induced fit” hypothesis 诱导契合假设
Typical example
Serine proteases
Trypsin胰蛋白酶: cleaves C-terminal side of basic amino acid residues (Arg, Lys)
Chymotrypsin 胰凝乳蛋白酶: cleaves C-terminal side of aromatic amino acid residues (Phe, Trp, Tyr)
H
Glyc ine 甘氨酸
COO-
CH
CH2OH Serine 丝氨酸
+H3N
COOCH CH2
+H3N
COOCH CH2
COO+H3N C H
COO+H3N C H
Βιβλιοθήκη Baidu
CH
CHOH
H3C CH3
CH3
Valine 颉氨酸
Threonine 苏氨酸
NH3+
COO-
CH
CH2 C CH
NH
Phenylalanine 苯丙氨酸
The “lock and key” hypothesis The “induced fit” hypothesis
There are two models of binding of a substrate to an enzyme
Lock-and-key model 锁和钥匙模型
Founder: Emil Fisher, 1894 Principle