Anaplerotic reactions
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2008-06-09T07:27:00Z
Littlealien182
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'''Anaplerotic reactions''' are those that form intermediates of the TCA or [[citric acid cycle]]. The [[malate]] is created by [[PEP carboxylase]] and [[malate dehydrogenase]] in the [[cytosol]]. Malate, in the [[mitochondrial matrix]], can be used to make [[pyruvate]] (catalyzed by [[NAD+ malic enzyme]]) or [[oxaloacetic acid]], both of which can enter the [[citric acid cycle]]. As this is a [[cycle]], formation of any of the intermediates can be used to 'top up' the whole cycle. Anaplerotic is of [[Ancient Greek|Greek]] origin, meaning ''to fill up''.
pyruvate carboxylase deficiency is an inherited metabolic disorder where anaplerosis is greatly reduced. Other anaplerortic substrates such as the odd-carbon containing triglyceride [[Triheptanoin]] is used to treat this disorder.
There are 4 reactions classed as anaplerotic, yet the production of oxaloacetate from pyruvate has probably the most physiologic importance.
{| class="wikitable"
| '''From''' || '''To''' || '''Reaction''' || '''Notes'''
|-
| [[Pyruvate]] || [[oxaloacetate]] || pyruvate + CO<sub>2</sub> + H<sub>2</sub>O + ATP <math>\longrightarrow</math> oxaloacetate + ADP + Pi + 2H<sup>+</sup> || This reaction is catalysed by [[pyruvate carboxylase]], an [[enzyme]] activated by [[Acetyl coenzyme A|Acetyl-CoA]], indicating a lack of [[oxaloacetate]].
[[Pyruvate]] can also be converted to [[malic acid|L-malate]], another intermediate, in a similar way.
|-
| [[Aspartate]] || [[oxaloacetate]] || - || This is a reversible reaction forming oxaloacetate from [[aspartate]] in a [[transamination]] reaction, via [[aspartate transaminase]].
|-
| [[Glutamate]] || α-[[ketoglutarate]]|| [[glutamate]] + NAD<sup>+</sup> + H<sub>2</sub>O <math>\longrightarrow</math> NH<sub>4</sub><sup>+</sup> + α-ketoglutarate + NADH + H<sup>+</sup>. || This reaction is catalysed by [[glutamate-dehydrogenase]].
|-
| [[β-oxidation]] of [[fatty acid]]s || [[succinyl-CoA]] || - || When odd-chain [[fatty acids]] are oxidized, one molecule of succinyl-CoA is formed per fatty acid. The final enzyme is [[methylmalonyl-CoA mutase]].
|}
==External links==
* {{cite journal |author=Owen O, Kalhan S, Hanson R |title=The key role of anaplerosis and cataplerosis for citric acid cycle function |journal=J. Biol. Chem. |volume=277 |issue=34 |pages=30409–12 |year=2002 |pmid=12087111 |url=http://www.jbc.org/cgi/content/full/277/34/30409 |doi=10.1074/jbc.R200006200}}
{{Citric acid cycle enzymes}}
[[Category:Cellular respiration]]
{{metabolism-stub}}
[[ca:Reacció anapleròtica]]
[[de:Anaplerotische Reaktionen]]
[[es:Reacciones anapleróticas]]