EC - O-phosphoserine—tRNA ligase

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IntEnz Enzyme Nomenclature


Accepted name:
O-phosphoserine—tRNA ligase
Other names:
non-canonical O-phosphoseryl-tRNA synthetase
O-phosphoseryl-tRNA ligase
Systematic name:
O-phospho-L-serine:tRNACys ligase (AMP-forming)



In organisms like Archaeoglobus fulgidus lacking EC (cysteine—tRNA ligase) for the direct Cys-tRNACys formation, Cys-tRNACys is produced by an indirect pathway, in which EC ligates O-phosphoserine to tRNACys, and EC (O-phospho-L-seryl-tRNA: Cys-tRNA synthase) converts the produced O-phospho-L-seryl-tRNACys to Cys-tRNACys. The SepRS/SepCysS pathway is the sole route for cysteine biosynthesis in the organism [1]. Methanosarcina mazei can use both pathways, the direct route using EC (cysteine—tRNA ligase) and the indirect pathway with EC and EC (O-phospho-L-seryl-tRNA: Cys-tRNA synthase) [2].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00363
Structural data: CSA , EC2PDB
UniProtKB/Swiss-Prot: (21) [show] [UniProt]


  1. Fukunaga, R., Yokoyama, S.
    Structural insights into the first step of RNA-dependent cysteine biosynthesis in archaea.
    Nat. Struct. Mol. Biol. 14: 272-279 (2007). [PMID: 17351629]
  2. Hauenstein, S. I., Perona, J. J.
    Redundant synthesis of cysteinyl-tRNACys in Methanosarcina mazei.
    J. Biol. Chem. 283: 22007-22017 (2008). [PMID: 18559341]

[EC created 2009]