Multienzyme systems

1
Multienzyme systems

• A soluble or dissociated multienzyme system
• with diffusing intermediates A, B, C

S
A
B
C
P
E1
E2
E3
E4
2
Multienzyme systems

• Multienzyme complex
• Intermediates in the reaction sequence catalyzed
  by an enzyme complex are covalently bound and do
  no diffuse away from the complex

E2
E7
E1
E3
E6
E4
E5
3
Multienzyme systems

• Membrane bound enzyme systems
• Large supramolar structures such as membranes or
  ribosomes
• Terminal oxydation chain

4
H
H
H
H
H
4 H
4 H
2 H




Cit c

III.
e-
I.
e-
UQ
e-
II.
IV.
e-
e-
-
-
-
-
NADH H
Szukcinát
4 H O2
Fumarát
NAD
H2O
5
Multienzyme systems

• Kinetical behaviour
• Each component has an own Km for substrate,
  cofactor, Vmax and pH optimum
• Computer modell
• Regulatory enzyme

• Fatty acid synthetase
• Pyruvate-dehydrogenase
• .a-ketoglutarate dehydrogenase
• Branched chain amino acid dehydrogenase

6
Pyruvate-dehydrogenase (PDH)
Glucose
glycolysis
Pyruvate
Pyruvate-dehydrogenase enzyme complex
7
Piruvát - dehidrogenáz
Kofaktorok
NAD
HS-CoA
Koenzimek
Tiamin-pirofoszfát (TPP)
Liponsav
Prosztetikus csoportok
FAD
8
A piruvát-dehidrogenáz multienzim komplex (PDH
komplex)
E1 Piruvát dehidrogenáz a2 b2 (20-30)
Protein-kináz
E2 Dihidrolipoil-transzacetiláz (60) x
alegység (6)
Foszfoprotein-foszfatáz
E3 Dihidrolipoil-dehidrogenáz (6)
X
E1 b
E2
E3
E1 a
TPP-
FAD
9
A PDH komplex szabályozása
aktív
ATP NADH H Acetil-CoA - Piruvát (máj)
X
Inzulin (zsírszövet)
E1 b
E2
E3
E1 a
HPO42-
ATP
PDH-kináz
PDH-foszfatáz
inaktív
ADP
H2O
X
Ca2 ADP, NAD HS-CoA koncentráció növekedése eset
én
E1 b
E2
E3
E1 a