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 220.127.116.11), but the reaction is more similar to that of O-phosphoserine sulfhydrylase (EC 18.104.22.168).
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]