FuzzyBot: Importing a new version from external source

2024-03-31T02:38:40Z

Importing a new version from external source

New page

== Steps ==
There are ten basic steps in the citric acid cycle, as outlined below. The cycle is continuously supplied with new carbon in the form of [[acetyl-CoA]], entering at step 0 in the table.
{| class="wikitable"
!
!Reaction type
!Substrates
!Enzyme
!Products
!Comment
|-
|{{nowrap|0 / 10}}
|[[Aldol condensation]]
|[[Oxaloacetic acid|Oxaloacetate]] + [[Acetyl CoA]] + H2O
|[[Citrate synthase]]
|[[Citric acid|Citrate]] + [[Coenzyme A|CoA-SH]]
|irreversible, extends the 4C [[Oxaloacetic acid|oxaloacetate]] to a 6C molecule
|-
|1
| [[Dehydration reaction|Dehydration]]
|[[Citrate]]
| rowspan="2" |[[Aconitase]]
|''[[Cis–trans isomerism|cis]]''-[[Aconitic acid|Aconitate]] + H2O
|rowspan=2|reversible [[Isomerization|isomerisation]]
|-
|2
|[[Hydration reaction|Hydration]]
|[[Aconitate|''cis''-Aconitate]] + H2O
|[[Isocitric acid|Isocitrate]]
|-
|3
|[[Oxidation]]
|[[Isocitrate]] + [[Nicotinamide adenine dinucleotide|NAD]]+
| rowspan="2" |[[Isocitrate dehydrogenase]]
|[[Oxalosuccinic acid|Oxalosuccinate]] + [[Nicotinamide adenine dinucleotide|NADH + H +]]
|generates [[NADH]] (equivalent of 2.5 ATP)
|-
|4
|[[Decarboxylation]]
|[[Oxalosuccinate]]
|[[alpha-Ketoglutaric acid|α-Ketoglutarate]] + CO2
|rate-limiting, irreversible stage, generates a 5C molecule
|-
|5
|Oxidative [[decarboxylation]]
|[[alpha-Ketoglutaric acid|α-Ketoglutarate]] + NAD+ + CoA-SH
|[[Alpha-ketoglutarate dehydrogenase|α-Ketoglutarate dehydrogenase]], [[Thiamine pyrophosphate]], [[Lipoic acid]], Mg++,transsuccinytase
|[[Succinyl-CoA]] + [[Nicotinamide adenine dinucleotide|NADH + H +]] + CO2
|irreversible stage, generates [[Nicotinamide adenine dinucleotide|NADH]] (equivalent of 2.5 ATP), regenerates the 4C chain (CoA excluded)
|-
|6
|[[substrate-level phosphorylation|substrate-level phosphorylation]]
|[[Succinyl-CoA]] + [[Guanosine diphosphate|GDP]] + [[Inorganic phosphate|Pi]]
|[[Succinyl coenzyme A synthetase|Succinyl-CoA synthetase]]
|[[Succinic acid|Succinate]] + CoA-SH + [[Guanosine triphosphate|GTP]]
|or [[adenosine diphosphate|ADP]]→[[adenosine triphosphate|ATP]] instead of GDP→GTP, generates 1 ATP or equivalent. [[Condensation reaction]] of [[Guanosine diphosphate|GDP]] + [[Inorganic phosphate|Pi]] and [[hydrolysis]] of [[succinyl-CoA]] involve the H2O needed for balanced equation.
|-
|7
|[[Redox|Oxidation]]
|[[Succinate]] + [[ubiquinone]] (Q)
|[[Succinate dehydrogenase]]
|[[Fumaric acid|Fumarate]] + [[ubiquinol]] (QH2)
|uses [[Flavin adenine dinucleotide|FAD]] as a [[prosthetic group]] (FAD→FADH2 in the first step of the reaction) in the enzyme. These two electrons are later transferred to QH2 during Complex II of the ETC, where they generate the equivalent of 1.5 ATP
|-
|8
|[[Hydration reaction|Hydration]]
|[[Fumarate]] + H2O
|[[Fumarase]]
|''L''-[[Malic acid|Malate]]
|Hydration of C-C double bond
|-
|9
|[[Redox|Oxidation]]
|[[Malate|L-Malate]] + NAD+
|[[Malate dehydrogenase]]
|[[Oxaloacetate]] + NADH + H+
|reversible (in fact, equilibrium favors malate), generates [[NADH]] (equivalent of 2.5 ATP)
|-
|10 / 0
|[[Aldol condensation]]
|[[Oxaloacetic acid|Oxaloacetate]] + [[Acetyl CoA]] + H2O
|[[Citrate synthase]]
|[[Citric acid|Citrate]] + [[Coenzyme A|CoA-SH]]
|This is the same as step 0 and restarts the cycle. The reaction is irreversible and extends the 4C oxaloacetate to a 6C molecule
|}

Translations:Citric acid cycle/10/en - Revision history

FuzzyBot: Importing a new version from external source