Cysteine lyase

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cysteine lyase
EC no.
CAS no.9079-86-1
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

The enzyme cysteine lyase (EC [1] catalyzes the chemical reaction

L-cysteine + sulfite L-cysteate + hydrogen sulfide

This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is L-cysteine hydrogen-sulfide-lyase (adding sulfite; L-cysteate-forming). Other names in common use include cysteine (sulfite) lyase, and L-cysteine hydrogen-sulfide-lyase (adding sulfite). This enzyme participates in cysteine and taurine metabolism. It employs one cofactor, pyridoxal phosphate.


Genes encoding cysteine lyase (CL) originated around 300 million years ago by a tandem gene duplication and neofunctionalization of cystathionine β-lyase (CBS) shortly after the split of mammalian and reptilian lineages. CL genes are found only in Sauropsida where they are involved in a metabolic pathway for sulfur metabolism in the chicken egg. [2]


  1. ^ Tolosa EA, Chepurnova NK, Khomutov RM, Severin ES (1969). "Reactions catalysed by cysteine lyase from the yolk sac of chicken embryo". Biochim. Biophys. Acta. 171 (2): 369–71. doi:10.1016/0005-2744(69)90174-0. PMID 5813025.
  2. ^ Malatesta M, Mori G, Acquotti D, Campanini B, Peracchi A, Antin PB, Percudani R (2020). "Birth of a pathway for sulfur metabolism in early amniote evolution". Nat Ecol Evol. 4 (9): 1239–1246. doi:10.1038/s41559-020-1232-4. PMC 8364350. PMID 32601391.