IUBMB Enzyme Nomenclature


Accepted name: cysteate synthase

Reaction: O-phospho-L-serine + sulfite = L-cysteate + phosphate

Other name(s): sulfite:O-phospho-L-serine sulfotransferase (phosphate-hydrolysing, L-cysteate-forming).

Systematic name: sulfite:O-phospho-L-serine sulfonotransferase (phosphate-hydrolysing, L-cysteate-forming).

Comments: A pyridoxal-phosphate protein. It is highly specific for O-phospho-L-serine and sulfite. The reaction proceeds through a dehydroalanine (2-aminoacrylic acid) intermediate. The enzyme from Methanosarcina acetivorans is evolutionarily related to threonine synthase (EC, but the reaction is more similar to that of O-phosphoserine sulfhydrylase (EC

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


1. Graham, D.E., Taylor, S.M., Wolf, R.Z. and Namboori, S.C. Convergent evolution of coenzyme M biosynthesis in the Methanosarcinales: cysteate synthase evolved from an ancestral threonine synthase. Biochem. J. 424 (2009) 467-478. [PMID: 19761441]

[EC created 2009]

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