Formation of Citrate, from acetyl-CoA and oxaloacetate
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Which enzyme catalyses this?
Citrate synthase
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How does it happen?
Oxaloactetate binding to citrate synthase, creates a binding site for the acetyl-CoA
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What is the second stage of the cycle?
Formation of Iso-Citrate, via cis-Aconitate
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Which enzyme catalyses this?
Aconitase
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How does it happen?
Removal of H2O from citrate forms cis-Aconitate. Addition of H2O to cis-Aconitate yields isocitrate
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What is the thrid stage of the cycle?
Oxidation of isocitrate to α-ketoglutarate and CO2
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Which enzyme catalyses this?
Isocitrate dehydrogenase
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How does it happen?
Oxidative decarboxylation of isocitrate. Mn2+ is needed to interact with the intermediate oxalosuccinate in the binding site
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What is the fourth stage?
Oxidation of α-ketoglutarate to succinyl-CoA and CO2
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Which enzyme catalyses this?
α-ketoglutarate dehydrogenase complex
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How does this happen?
Another oxidative decarboxylation
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What is the fifth stage?
Conversion of succinyl-CoA to succinate
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Which enzyme catalyses?
succinyl-CoA synthetase (or succinic thiokinase)
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Sixth stage?
Oxidation of succinate to fumarate
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Which enzyme?
succinate dehydrogenase
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How?
oxidation of succinate
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Seventh stage?
Hydration of fumarate to malate
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Which enzyme?
fumarase
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How?
reversible hydration of fumarate to L-Malate
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Eighth stage?
Oxidation of malate to oxaloacetate
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Which enzyme?
malate dehydrogenase
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How?
oxidation of malate. Oxaloacetate is continuously removed by stage 1 (citrate formation), keeping the concentration of oxaloacetate low, pulling the equilibrium towards the re-formation of oxaloacetate
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How many NADH are released in each turn of the cycle?
3, 1 at step 3, 1 at step 4 and 1 at step 8
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How many FADH2 are released?
1, at step 6
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How many GTP/ATP are released?
1, at step 5
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How many NADH are released from each glucose molecule?
6 - 3 in each turn of the cycle, which uses one pyruvate molecule - two pyruvate from each glucose
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How many FADH2 are released from each glucose molecule?
2 - one from each pyruvate molecule
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How many ATP are released from each glucose molecule?
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