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B6db activities:
Description L-cystine β-lyase
Alternative names cystine C-S lyase;
Catalyzed reaction L-cystine + H(2)O = L-thiocysteine + pyruvate + NH(3) (overall reaction)
(1a) L-cystine = L-thiocysteine + 2-aminoprop-2-enoate
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)
Cofactor Pyridoxal-phosphate.
Comments The enzyme cleaves a carbon-sulfur bond, releasing L-thiocysteine and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. The latter reaction, which can occur spontaneously, can also be catalysed by EC, 2-iminobutanoate/2-iminopropanoate deaminase. The enzyme from Brassica oleracea var. italica (broccoli) does not act on cysteine or cystathionine.
Different from cysteine desulfurase (EC, in that the favorite substrate is cystine and the product persulfide is not protein-bound.

The reaction is carried out also by cystathionine beta-lyase (EC

Cystine lyase enzymes have been described in cyanobacteria (C-DES) and in plants.

Organisms -Eubacteria -Plants


Links Enzyme (activities)
BRENDA (activities)
KEGG (pathways)
PLPMDB (PLP mutants)
 Munt O, Prüfer D, Schulze Gronover C. (2013) A novel C-S lyase from the latex-producing plant Taraxacum brevicorniculatum displays alanine aminotransferase and l-cystine lyase activity. J Plant Physiol. 170 33-40.

 Kessler D. (2006) Slr0077 of Synechocystis has cysteine desulfurase as well as cystine lyase activity Biochem Biophys Res Commun 320 571-7.

 Jones, P.R.; Manabe, T.; Awazuhara, M.; Saito, K. (2003) A new member of plant CS-lyases. A cystine lyase from Arabidopsis thaliana J Biol Chem 278 10291-6.

 Kaiser, J.T.; Bruno, S.; Clausen, T.; Huber, R.; Schiaretti, F.; Mozzarelli, A.; Kessler, D. (2003) Snapshots of the cystine lyase C-DES during catalysis. Studies in solution and in the crystalline state J Biol Chem 278 357-65.

 Lang, T.; Kessler, D. (1999) Evidence for cysteine persulfide as reaction product of L-Cyst(e)ine C-S-lyase (C-DES) from Synechocystis. Analyses using cystine analogues and recombinant C-DES J Biol Chem 274 189-95.

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last changed 2018/03/21 13:08

B6db activities