| class="wikitable" style="text-align:center"
|+ L-Cysteine consumption pathways |
| Enzyme | → | Products
!Cofactor/Additional Reactant |
|---|
cysteine dioxygenase[{{cite journal | vauthors = Stipanuk MH, Ueki I, Dominy JE, Simmons CR, Hirschberger LL | title = Cysteine dioxygenase: a robust system for regulation of cellular cysteine levels | journal = Amino Acids | volume = 37 | issue = 1 | pages = 55–63 | date = May 2009 | pmid = 19011731 | pmc = 2736881 | doi = 10.1007/s00726-008-0202-y }}] | → | cysteine sulfinic acid
|iron |
serine racemase[{{cite journal | vauthors = Roychaudhuri R | title = Mammalian D-Cysteine: A new addition to the growing family of biologically relevant D-amino acids | journal = Chirality | pages = chir.23555 | date = March 2023 | pmid = 36890664 | doi = 10.1002/chir.23555 | s2cid = 257426578 }}] | → | D-cysteine
|pyridoxal phosphate |
cysteine lyase[{{cite journal | vauthors = Tolosa EA, Chepurnova NK, Khomutov RM, Severin ES | title = Reactions catalysed by cysteine lyase from the yolk sac of chicken embryo | journal = Biochimica et Biophysica Acta (BBA) - Enzymology | volume = 171 | issue = 2 | pages = 369–371 | date = February 1969 | pmid = 5813025 | doi = 10.1016/0005-2744(69)90174-0 | doi-access = free }}] | → | L-cysteate/hydrogen sulfide
|pyridoxal phosphate/sulfite |
cystathionine γ-lyase[{{cite journal | vauthors = Sun Q, Collins R, Huang S, Holmberg-Schiavone L, Anand GS, Tan CH, van-den-Berg S, Deng LW, Moore PK, Karlberg T, Sivaraman J | display-authors = 6 | title = Structural basis for the inhibition mechanism of human cystathionine gamma-lyase, an enzyme responsible for the production of H(2)S | language = English | journal = The Journal of Biological Chemistry | volume = 284 | issue = 5 | pages = 3076–3085 | date = January 2009 | pmid = 19019829 | doi = 10.1074/jbc.M805459200 | doi-access = free }}] | → | pyruvate/NH3/H2S
|pyridoxal phosphate |
cysteine—tRNA ligase[{{cite journal | vauthors = Mccorquodale DJ | title = The separation and partial purification of aminoacyl-RNA synthetases from Escherichia coli | journal = Biochimica et Biophysica Acta (BBA) - Specialized Section on Nucleic Acids and Related Subjects | volume = 91 | issue = 4 | pages = 541–548 | date = December 1964 | pmid = 14262440 | doi = 10.1016/0926-6550(64)90001-5 }}] | → | L-cysteinyl-tRNACys
| |
cystine reductase[{{cite journal | vauthors = Maresca B, Jacobson E, Medoff G, Kobayashi G | title = Cystine reductase in the dimorphic fungus Histoplasma capsulatum | journal = Journal of Bacteriology | volume = 135 | issue = 3 | pages = 987–992 | date = September 1978 | pmid = 211119 | pmc = 222474 | doi = 10.1128/jb.135.3.987-992.1978 }}] | → | L-cystine/NADH and H+
|NAD+ |
cysteine transaminase[{{cite journal | vauthors = Hipólito A, Nunes SC, Vicente JB, Serpa J | title = Cysteine Aminotransferase (CAT): A Pivotal Sponsor in Metabolic Remodeling and an Ally of 3-Mercaptopyruvate Sulfurtransferase (MST) in Cancer | journal = Molecules | volume = 25 | issue = 17 | pages = 3984 | date = September 2020 | pmid = 32882966 | pmc = 7504796 | doi = 10.3390/molecules25173984 | doi-access = free }}] | → | 3-mercapto-pyruvate/L-glutamate
|pyridoxal phosphate/alpha-ketoglutaric acid |
glutamate–cysteine ligase[{{cite journal | vauthors = Chen Y, Shertzer HG, Schneider SN, Nebert DW, Dalton TP | title = Glutamate cysteine ligase catalysis: dependence on ATP and modifier subunit for regulation of tissue glutathione levels | language = English | journal = The Journal of Biological Chemistry | volume = 280 | issue = 40 | pages = 33766–33774 | date = October 2005 | pmid = 16081425 | doi = 10.1074/jbc.M504604200 | doi-access = free }}]
|→
|γ-glutamyl cysteine/ADP and Pi
|ATP |
| class="wikitable" style="text-align:center"
|+ L-cysteine production pathways |
| Reactants
!→
!Enzyme | Cofactors
!Notes |
|---|
| O-acetyl-L-serine/hydrogen sulfide
|→
|cysteine synthase[{{cite journal | vauthors = Kredich NM, Becker MA, Tomkins GM | title = Purification and characterization of cysteine synthetase, a bifunctional protein complex, from Salmonella typhimurium | journal = The Journal of Biological Chemistry | volume = 244 | issue = 9 | pages = 2428–2439 | date = May 1969 | doi = 10.1016/S0021-9258(19)78241-6 | pmid = 4977445 | doi-access = free }}] | pyridoxal phosphate
|not present in humans |
| L-cystine/2 glutathione
|→
|glutathione-cystine transhydrogenase[{{cite journal | vauthors = Nagai S, Black S | title = A thiol-disulfide transhydrogenase from yeast | journal = The Journal of Biological Chemistry | volume = 243 | issue = 8 | pages = 1942–1947 | date = April 1968 | doi = 10.1016/S0021-9258(18)93532-5 | pmid = 5646485 | doi-access = free }}] | | |
| cystathionine
|→
|cystathionine γ-lyase | pyridoxal phosphate
| |
| 3-mercapto-pyruvate
|→
|cysteine transaminase | pyridoxal phosphate
| |