Cysteine metabolism
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Cysteine metabolism is comprised of the biological pathways that consume or create cysteine. The pathways of different amino acids and other metabolites interweave and overlap to creating complex systems.
[edit] 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.
| 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-tRNACys |
| 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.
| starting chemical | → | enzyme |
|---|---|---|
| O-acetyl-L-serine | → | cysteine synthase |
| L-cystine | → | glutathione-cystine transhydrogenase |
| pyruvate | → | cystathionine γ-lyase |
| 3-mercapto-pyruvate | → | cysteine transaminase |
