Download Oxidative decarboxylation of pyruvate

OXIDATIVE DECARBOXYLATION
OF PYRUVATE
Matrix of the mitochondria
contains pyruvate
dehydrogenase complex
The fate of glucose molecule in the cell
Synthesis of
glycogen
Glucose
Glucose-6phosphate
Glycogen
Pentose phosphate
pathway
Ribose, NADPH
Degradation of
glycogen
Gluconeogenesis
Glycolysis
Ethanol
Pyruvate
Acetyl Co A
Lactate
OXIDATIVE DECARBOXYLATION OF PYRUVATE
Only about 7 % of the total potential energy present in
glucose is released in glycolysis.
Glycolysis is preliminary phase, preparing glucose for
entry into aerobic metabolism.
Pyruvate formed in the aerobic conditions undergoes
conversion to acetyl CoA by pyruvate dehydrogenase
complex.
Pyruvate dehydrogenase complex is a bridge between
glycolysis and aerobic metabolism – citric acid cycle.
Pyruvate dehydrogenase complex and enzymes of
cytric acid cycle are located in the matrix of
mitochondria.
Entry of Pyruvate into the Mitochondrion
Pyruvate freely diffuses through the outer membrane of mitochondria through the channels formed by transmembrane proteins porins.
Pyruvate translocase, protein embedded into the inner
membrane, transports pyruvate from the intermembrane space
into the matrix in symport with H+ and exchange (antiport) for
OH-.
Conversion of Pyruvate to Acetyl CoA
• Pyruvate dehydrogenase complex (PDH complex) is
a multienzyme complex containing 3 enzymes, 5
coenzymes and other proteins.
Pyruvate
dehydrogenase
complex is giant,
with molecular
mass ranging
from 4 to 10
million daltons.
Electron micrograph of the
pyruvate dehydrogenase
complex from E. coli.
Enzymes:
E1 = pyruvate dehydrogenase
E2 = dihydrolipoyl acetyltransferase
E3 = dihydrolipoyl dehydrogenase
Coenzymes: TPP (thiamine pyrophosphate),
lipoamide, HS-CoA, FAD+, NAD+.
TPP is a prosthetic group of B1;
lipoamide is a prosthetic group of B2; and
FAD is a prosthetic group of B3.
The building block of
TPP is vitamin B1 (thiamin);
NAD – vitamin B5 (nicotinamide);
FAD – vitamin B2 (riboflavin),
HS-CoA – vitamin B3 (pantothenic acid),
lipoamide – lipoic acid
Pyruvate dehydrogenase complex is a classic example of
multienzyme complex
Overall reaction of pyruvate dehydrogenase complex
The oxidative decarboxylation of pyruvate catalized by
pyruvate dehydrogenase complex occurs in five steps.