IUBMB Enzyme Nomenclature


Accepted name: [CysO sulfur-carrier protein]-thiocarboxylate-dependent cysteine synthase

Reaction: O-phospho-L-serine + [CysO sulfur-carrier protein]-Gly-NH-CH2-C(O)SH = [CysO sulfur-carrier protein]-Gly-NH-CH2-C(O)-S-L-cysteine + phosphate

Other name(s): CysM

Systematic name: O-phospho-L-serine:thiocarboxylated [CysO sulfur-carrier protein] 2-amino-2-carboxyethyltransferase

Comments: A pyridoxal-phosphate protein. The enzyme participates in an alternative pathway for L-cysteine biosynthesis that involves a protein-bound thiocarboxylate as the sulfide donor. The enzyme from the bacterium Mycobacterium tuberculosis also has very low activity with O3-acetyl-L-serine (cf. EC, O-phosphoserine sulfhydrylase).

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. O'Leary, S.E., Jurgenson, C.T., Ealick, S.E. and Begley, T.P. O-Phospho-L-serine and the thiocarboxylated sulfur carrier protein CysO-COSH are substrates for CysM, a cysteine synthase from Mycobacterium tuberculosis. Biochemistry 47 (2008) 11606-11615. [PMID: 18842002]

2. Jurgenson, C.T., Burns, K.E., Begley, T.P. and Ealick, S.E. Crystal structure of a sulfur carrier protein complex found in the cysteine biosynthetic pathway of Mycobacterium tuberculosis. Biochemistry 47 (2008) 10354-10364. [PMID: 18771296]

3. Ågren, D., Schnell, R., Oehlmann, W., Singh, M. and Schneider, G. Cysteine synthase (CysM) of Mycobacterium tuberculosis is an O-phosphoserine sulfhydrylase: evidence for an alternative cysteine biosynthesis pathway in mycobacteria. J. Biol. Chem. 283 (2008) 31567-31574. [PMID: 18799456]

4. Ågren, D., Schnell, R. and Schneider, G. The C-terminal of CysM from Mycobacterium tuberculosis protects the aminoacrylate intermediate and is involved in sulfur donor selectivity. FEBS Lett 583 (2009) 330-336. [PMID: 19101553]

[EC created 2013]

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