Cysteine metabolism
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2008-05-24T18:33:56Z
Neuron1
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improved readability of first setnence
{{Cleanup|date=September 2006}}
'''Cysteine metabolism''' refers to the biological pathways that consume or create [[cysteine]]. The pathways of different amino acids and other metabolites interweave and overlap to creating complex systems.
==Human cysteine metabolism==
In human cysteine metabolism, L-cysteine is consumed in several ways as shown below. L-cysteine is also consumed in [[methionine]] and [[glutathione]] metabolism as well as [[pantothenate]]/[[CoA]] biosynthesis.
{| class="wikitable" style="text-align:center"
|+ '''L-cysteine consumption pathways'''
|-
! enzyme !! → !! product
|-
| [[cysteine dioxygenase]] || → || 3-sulfino-L-alanine (or [[cysteine sulfinic acid]])
|-
| [[amino-acid racemase]] || → || D-cysteine
|-
| [[cysteine lyase]] || → || [[L-cysteate]]
|-
| [[cysteine—tRNA ligase]] || → || L-cysteinyl-tRNA<sup>Cys</sup>
|-
| [[cystine reductase]] || → || L-[[cystine]]
|-
| [[cysteine transaminase]] || → || [[3-mercapto-pyruvate]]
|}
L-cysteine is the product of several processes as well. In addition to the reactions below, L-cysteine is also a product of [[glycine]], [[serine]], and [[threonine]] metabolism.
{| class="wikitable" style="text-align:center"
|+ '''L-cysteine production pathways'''
|-
! starting chemical !! → !! enzyme
|-
| [[O-acetyl-L-serine]] || → || [[cysteine synthase]]
|-
| L-[[cystine]] || → || [[glutathione-cystine transhydrogenase]]
|-
| [[pyruvate]] || → || [[cystathionine γ-lyase]]
|-
| [[3-mercapto-pyruvate]] || → || [[cysteine transaminase]]
|}
==See also==
* [[D-cysteine desulfhydrase]]
[[Category:Sulfur metabolism]]
[[Category:Sulfur amino acids]]