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Citric acid cycle
Production of acetyl-CoAReactions of citric acid cycle
Regulation of the citric acid cycle
Oxidative decarboxylation
P. 602
Production of acetyl-CoA is catalyzed by a large enzyme complex
NAD+ O IICH3-C-S-CoA
CoA-SH
TPP-CHOH-CH3
CO2
pyruvate
Reactions catalyze by PDH (pyruvate dehydrogenase
complex)
Pyruvate dehydro-genase
(E1)
TPP
LysDihydrolipoyl
transacetylase(E2)
(o)lipoate O
II
CH
3 -C-lipoate (r)lipoate
Acetyl-CoA
E3
FADH2FAD
NADH
TPP lipoate CoA FAD NAD+
P. 570
Pyruvate dehydrogenase complex
• Pyruvate dehydrogenase complex includes three enzymes: pyruvate dehydrogenase (E1), dihydrolipoyl transacetylase (E2), and dihydrolipoyl dehydrogenase (E3) and also five coenzymes.
P. 513NAD+
CAC
TPP
p.541
PDH
P. 516FAD and FMN
PDH
P. 603
Coenzyme A (CoA)
PDH
P. 603
Lipoic acid (lipoate)
• Together with lysine of E2, the lipoyllysyl arm has enable the E2 becoming more flexible in terms of catalyzing reactions.
PDH
The citric acid cycle
oxaloacetate
Acetyl-CoA
H2O
CoA-SHCitrate
isocitrate
H2OH2O
cis-aconitate
citrate
cis-aconitate
isocitrate NAD+
NADHCO2-ketoglutarate
-ketoglutarate
NAD+
CoA-SH
CO2NADHSuccinyl-CoASuccinyl-CoA
GDP(ADP)
GTP(ATP)
Pi
CoA-SHSuccinate
SuccinateFAD
FADH2Fumarate
Fumarate
malateH2O
malate
NAD+NADHoxaloacetate
Citrate synthase
aconitase
aconitase
Isocitrate dehydrogenase
a-ketoglutarate dehydrogenase
complex
Succinyl-CoA synthetase
Succinate dehydrogenase
Fumarase
Malate dehydrogenase
p617Citric acid cycle components are important biosynthetic intermediates
Anaplerotic reactions of citric acid cycle
Regulation of citric acid cycle
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