Citric Acid Cycle
rename
Updated
2009-03-04 08:54
Citric Acid Cycle
The Citric Acid Cycle is also known as the Tricarboxylic Acid Cycle (TCA cycle),the Krebs cycle, or, rarely, the Szent-Györgyi–Krebs cycle.
Citric Acid/Citrate is not Vitamin C. Vitamin C is Ascorbic Acid/Ascorbate.
| Step/Reaction | Enzyme (Prosthetic Group) |
|---|---|
| (1) Acetyl CoA + Oxaloacetate + H2O -> Citrate + CoA + H+ | Citrate Synthetase |
| (2) Citrate <=> cis-Aconitate + H2O | Aconitase (Fe-S) |
| (3) cis-Aconitate + H2O <=> Isocitrate | Aconitase (Fe-S) |
| (4) Isocitrate + NAD+ <=> α-Ketoglutarate + CO2 + NADH | Isocitrate Dehydrogenase (Lipoic Acid, FAD) |
| (5) α-Ketoglutarate + NAD+ + CoA <=> Succinyl CoA + CO2 + NADH | α-Ketoglutarate Dehydrogenase Complex (TPP) |
| (6) Succinyl CoA + Pi + GDP <=> Succinate + GTP + CoA | Succinyl CoA Synthetase |
| (7) Succinate +FAD (enzyme-bound) <=> Fumarate + FADH2 (enzyme-bound) | Succinate Dehydrogenase (FAD, Fe-S) |
| (8) Fumarate + H2O <=> L-Malate | Fumarase |
| (9) L-Malate + NAD+ <=> Oxaloacetate + NADH + H+ | Malate Dehydrogenase |
Pyruvate Dehydrogenase Complex of E. Coli
| Reaction | Enzyme (Prosthetic Group) |
|---|---|
| Oxidative Decarboxylation of Pyruvate | Pyruvate Dehydrogenase Component (TPP) |
| Transfer of the Acetyl Group to CoA | Dihydrolipoyl Transacetylase (Lipoamide) |
| Regeneration of the Oxidized Form of Lipoamide | Dihydrolipoyl Dehydrogenase (FAD) |
