C8 Enzime
-
Upload
andreea-pop -
Category
Documents
-
view
228 -
download
0
Transcript of C8 Enzime
![Page 1: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/1.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 1/38
Enzime
![Page 2: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/2.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 2/38
Enzimele - biocatalizatori
Caracteristici comune cuchemocatalizatorii
• Măresc viteza de reacție pe
seama reducerii energiei de
activare• Nu modifică constanta de
echilibru a unei reacții
reversibile
• Acționează în cantități mici • La sfârșitul reacției se
regăsesc neschimbate*
Carcteristici particulare aleenzimelor
• Activitate
• Selectivitate
• Condiții blânde de reacție
• Deplină compatibilitate cu
mediul
• Pot fi obiectul reglării
• Pot fi utilizate „ex vivo”
![Page 3: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/3.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 3/38
• Reactii de transfer de electroni1. Oxidoreductaze
• Reacții de transfer de diferite grupări 2. Transferaze
• Reacții de rupere hidrolitica a unor legături3. Hidrolaze
• Reacții de adiție / eliminare 4. Liaze
• Reacții de izomerizare 5. Izomeraze
• Reacții de condensare 6. Ligaze (Sintetaze)
Clasificarea enzimelor
![Page 4: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/4.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 4/38
Ex. E.C. 1.1.1.1 Alcool dehidrogenzaza
1. Clasa : oxidoreductaze
1. Subclasa: donor de electroni CH-OH
1. Subsubclasa acceptorul de electroni1. Enzima 1
Codificarea enzimelor
![Page 5: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/5.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 5/38
1. Modelul lacăt – cheie
(lock-key)Emil Fischer 1894
• Presupune o conformaţie rigidă a enzimei.
• Nu explică: – Selectivitatea largă de substrat
– Faptul că enzimele care catalizează transformarea substratuilor
voluminoase au eficienţă mai redusă fată de substraturile mici
Emil Fischer
(1852 – 1919)
![Page 6: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/6.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 6/38
2. Modelul ataşării prin trei puncte
Ogston (1948)
Explică stereoselectivitatea prin atașarea cea mai
stabilă (trei puncte) a eutomerului
Al. George Ogston1911-1996
![Page 7: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/7.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 7/38
3. Modelul ajustării induse
(induced fit) Koshland 1960
La apropierea glucozei (roşu) de hexokinază (albastru) aceasta îşi schimbă
conformaţia pentru a putea include molecula de glucoză în situsul catalitic
– Explică necesitatea unor caracteristrici structuralesuplimentare fată de grupele reactive din substrat
– Explică selectivitatea largă de substrat a unor enzime
Daniel KOSHLAND
1920-2007
![Page 8: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/8.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 8/38
4. Modelul desolvatării
solvatării-substituţiei (Dewar
(1986)
• Cinetica enzimatică similară cineticii in fazăgazoasă
• Substratul substituie apa din situsul catalitic
• Grupările reactive din substrat şi din enzimăinteracţionează fără perturbaţia provocatăde apă
• Explică de ce substratuile mici suntconvertite cu viteză mai mică decâtsubstratuile voluminoase, din cauza faptuluică acestea nu pot substitui întreaga
cantitate de apă din situsul catalitic
M.J.DEWAR1918-1997
![Page 9: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/9.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 9/38
Reactie
necatalitică
Reactie
enzimatică
![Page 10: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/10.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 10/38
Destabilizarea complexului ES
Ecuaţia lui Kurz
n n T
e Se
k K K
k K K
E+S E+P
ES E+PET=
K S K T
E+T=
K e
=
=K n
k e
k n
E+S
ES
E+P
EP
ES
=
G=
e
E+S ES ES=
E+P
Transformare
enzimatica
coordonata de reactie
Gdest Ecuaţia lui KURTZ
![Page 11: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/11.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 11/38
n ev [T ] şi v [ET ]
n e
[E][T ] [ET ]K , respectiv K
[E][S] [ES]
E+S E+P
ES E+PET=
K S K T
E+T=
K e
=
=K n
k e
k n
B B
n n e e
k T k T
k K respectiv k K h h
e e
n n
k K
k K
S T
[E][S] [E][T ]K iar K
[ES] [ET ]
k e
k n=
Ke≠
Kn≠
=ET
≠E S
ES E T≠ =
K
K
![Page 12: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/12.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 12/38
Analogii plani ai prolinei, sunt inhibitori ai prolin racemazei. Legarea acestora la
Situsul catalitic al enzimei se face de 160 de ori mai puternic decât în cazul prolinei
![Page 13: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/13.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 13/38
S
P2
k2
k1
Selectivitate de produs
P2
Biocatalizator
chemo-regio-Stereo- -enatiomer(top)- -diastereomer(top)-
selectivitate
- geometric
Selectivitatea
(bio)catalizatorilor
Selectivitate de substrat(specificitate)
S1
S2
P1
P2
Biocatalizator
k1
k2
![Page 14: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/14.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 14/38
A1
A2
X1
X2
k1
k2
Substrat
A1 A2
X1 A2
X2A1
k1
k2
Produs
Chemoselectivitate
![Page 15: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/15.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 15/38
A X
k1
k2
Substrat
A X
k1
k2
Produs
A A
A
X
A
X
Regioselectivitate
![Page 16: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/16.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 16/38
Enantioselectivitate
k1
k2
Produs = selectivitate enantioptopa
(asimetrizarean substratului)
A
C D
C D
A A
C D
X B
C D
B X
C D
X B
C D
B X
k1
k2
fete enantiotope
grupe enantitope
Conversia maxima raportata la eutomer:50 %
k1
k2
Substrat : selectivitate enantiomera
C D
A B
C D
B X
C D
X B
C D
B A
![Page 17: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/17.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 17/38
Diastereoselectivitate
Conversia maxima raportata la eutomer:50 %
k1
k2
Substrat = selectivitate diastereomera
C* D
A B
C* D
B X
C* D
X B
C* D
B A
k1
k2
Produs = selectivitate diastereoptopa
A
C* D
C* D
A A
C* D
X B
C* D
B X
C* D
X B
C* D
B X
k1
k2
fete diastereotope
grupe diastereotope
![Page 18: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/18.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 18/38
Bazele cinetice ale selectivităţii
S
P1
P2
S1
S2
P1
P2
k1
k2
k1
k2
k1>k2 [P1] > [P2]
S
ET1
ET2
E+P1 E+P2
G1
G2
[P1] > [P2]
![Page 19: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/19.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 19/38
1. Efectul de proximitate
![Page 20: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/20.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 20/38
Efectul de
Proximitate
(cont)
![Page 21: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/21.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 21/38
![Page 22: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/22.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 22/38
2. Cataliza acido-
bazică
![Page 23: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/23.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 23/38
R O P
O
OR 1
O-
Enz-Y
R O P OR 1
O-
Enz-Y
O-
R O P
O
O-
Enz-Y
Enz-Y
O
OH
HOHO
OH
X
Enz-Y
O
OH
HOHO
OH
Y-Enz
R C
O
X R C
O-
X
Enz-Y
R C
O
Enz-Y
Fosforil-enzim
Acil-enzimă
Glucozil-enzimă
S1 X
Enz
X
S1 Enz
Enz
S2
S1 S2
intermediar covalent
3. Formare de
Intermediari
covalenţi
![Page 24: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/24.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 24/38
4. Cataliza prin ioni metalici
1. Stabilizare de sarcini negative prin vacanţele orbitale ale ionilor
metalelor tranziţionale 2. Generare de nucleofili în condiţii fiziologice date
Anhidraza carbonică
![Page 25: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/25.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 25/38
NHNHN
H
H
H2N NH2
NH
C
CH3
O O
O
NNH H
O C H
CH3
O O
NH
H2N NH2
NH
Piruvat Lactat
Histidina NAD+
Arginina
Interacţiunea enzimă - substrat
Aminoacizicontact
auxiliari
conformaţionali
neutri
![Page 26: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/26.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 26/38
Situsul catalitic şi mecanismul alcool
dehidrogenazei din Saccharomyces cerevisiae
HR
HS N
CONH2
O
Zn+2 SCys
CysS
His
fata " Re" fata "Si"
OHH
LS
S
Regula lui Prelog S
L
![Page 27: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/27.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 27/38
acil enzimă intermediar tetraedric Complex enzimă produs
C
R 2H
O
O
OH N NH
O
O
C
O
O
C H H N N
C
R 2
O
H
O
O- N NH
H
O
H
C
R 2
O
O
O
O
C
complex enzimă-substrat intermediar tetraedric acil enzimă
grupă fugace
N NH
C
R 2
O
O
O
O
C
NH2R 1
O
O
C H N N H
N C
R 2
O-
H
R 1
O
N C
R 2
O
H
R 1
N NH OH
O
O
1 1
11
1
1
1 2
5 4
3
6
Mecanismul de acţiune al serin hidrolazelor
Lipaze, chimotripsina, tripsina, subtilizina,
![Page 28: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/28.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 28/38
Mecanismul de acţiune al proteazelor aspartice
Pepsina, chimozina, renina, proteaza HIV-1,
![Page 29: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/29.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 29/38
![Page 30: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/30.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 30/38
Tiamina (Vitamina B1) și tiaminpirofosfatul
![Page 31: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/31.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 31/38
H3C
CO
OH
CH3
CO2-
HOPO3-2
Acetilfosfat
H3C
C
O
OPO3-2
H2O
Acetat
H3C
C
O
O-
[O]
C
O
H3C R1
CH3
S
NR2
a
a
a
Aceta ldehidă
H3C
C
O
H
(H+)
C
O
H3C R1
CH3
S
NR2
HH
Acetolactat
H3C C
O
CO2-
H3C CHO
C
O
H3C R1
CH3
S
NR2
C
HO
CH3H
CO2- Acetoina
H3C
C
O CH
OH
CH3C
O
H3C R1
CH3
S
NR2
CH
HO
CH3H
- CO2
C
HO
H3CR1
CH3
S
NR2
C
HO
H3C R1
CH3
S
NR2
C
HOC
O
O-
H3C R1
CH3
S
NR2
Piruvat
(H+)CO
C
O
O-
CH3
R2 ==R1
N
NH3C
CH2
NH2
(CH2)2 O
P O
P OH
O O-
-O
O
R2
N
S
CH3
R1
![Page 32: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/32.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 32/38
B
R2
N
S
CH3
R1
(H+)
CHO
CH OH
CH2OPO3-2
Aldehidă 3-fosfoglicerică (APG)
R2
N
S
CH3
R1
OHC
CH2OH
CH
CH
CH
CH OH
CH2OPO3-2
O
OH
OH
D-Ribozo-5-fosfat
R2
N
S
CH3
R1
H+
D-Sedoheptulozo-7-fosfat N
NH3C
CH2
NH2
R2 =
R1 = (CH2)2 O
P-O O
O
P-O
O
OH
BH
R2
N
S
CH3
R1
OC
CH2OH
OH
OH
CH2OPO3-2
OHCH
CH
CH
CHHO
H
CH2OH
C O
CHHO
CH OH
CH2OPO3-2
D-Xilulozo-5-fosfat
R2N
S
CH3
R1
CH2OPO3-2
OHCH
O CH
OHC
CH2OH
H
R2
N
S
CH3
R1
OHC
CH2OH
OC
CH2OH
OH
OH
CH2OPO3-2
OHCH
CH
CH
CHHO
Mecanismul transcetolazelor
![Page 33: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/33.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 33/38
Cofactori flavinici
![Page 34: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/34.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 34/38
Comportamentul redox al structurilor flavinice
![Page 35: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/35.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 35/38
Reacția cu oxigenul
Reacția Bayer-Villiger
e-caprolactona
Cofactori PLP
![Page 36: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/36.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 36/38
Inversie configuraţională
Decarboxilare
Cofactori PLP
Reacția de transaminare
![Page 37: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/37.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 37/38
Reacția de transaminare
![Page 38: C8 Enzime](https://reader034.fdocumente.com/reader034/viewer/2022052216/577cc1981a28aba71193671f/html5/thumbnails/38.jpg)
8/10/2019 C8 Enzime
http://slidepdf.com/reader/full/c8-enzime 38/38
-O
CO
O
PO3-2
NH
NH S
O
H2C
O
SCoA
domeniu
biotincarboxilazic
domeniu
transcarboxilazic
proteina purtatoare decarboxibiotina
Biotina
(biotin carboxilaze)