Cysteine metabolism
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,[pantothenate/coenzyme A biosynthesis.
Enzyme | → | Products | Cofactor/Additional Reactant |
---|---|---|---|
cysteine dioxygenase[1] | → | cysteine sulfinic acid | iron |
serine racemase[2] | → | D-cysteine | pyridoxal phosphate |
cysteine lyase[3] | → | L-cysteate/hydrogen sulfide | pyridoxal phosphate/sulfite |
cystathionine γ-lyase[4] |
→ | pyruvate/NH3/H2S | pyridoxal phosphate |
cysteine—tRNA ligase[5] | → | L-cysteinyl-tRNACys | |
cystine reductase[6] | → | L-cystine/NADH and H+ | NAD+ |
cysteine transaminase[7] | → | 3-mercapto-pyruvate /L-glutamate
|
pyridoxal phosphate/alpha-ketoglutaric acid |
glutamate–cysteine ligase[8] | → | γ-glutamyl cysteine/ADP and Pi | ATP |
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.
Reactants | → | Enzyme | Cofactors | Notes |
---|---|---|---|---|
O-acetyl-L-serine/hydrogen sulfide | → | cysteine synthase[9] | pyridoxal phosphate | not present in humans |
L-cystine/2 glutathione | → | glutathione-cystine transhydrogenase[10] |
||
cystathionine | → | cystathionine γ-lyase[4] |
pyridoxal phosphate | |
3-mercapto-pyruvate
|
→ | cysteine transaminase[7] | pyridoxal phosphate |