O-phospho-L-serine—tRNA ligase

{{Infobox enzyme

| Name = O-Phospho-L-serine—tRNA ligase

| EC_number = 6.1.1.27

| CAS_number =

| GO_code =

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O-phospho-L-serine—tRNA ligase ({{EnzExplorer|6.1.1.27}}, O-phosphoseryl-tRNA ligase, non-canonical O-phosphoseryl-tRNA synthetase, SepRS) is an enzyme with systematic name O-phospho-L-serine:tRNACys ligase (AMP-forming).{{cite journal | vauthors = Fukunaga R, Yokoyama S | title = Structural insights into the first step of RNA-dependent cysteine biosynthesis in archaea | journal = Nature Structural & Molecular Biology | volume = 14 | issue = 4 | pages = 272–9 | date = April 2007 | pmid = 17351629 | doi = 10.1038/nsmb1219 | s2cid = 10959763 }}{{cite journal | vauthors = Hauenstein SI, Perona JJ | title = Redundant synthesis of cysteinyl-tRNACys in Methanosarcina mazei | journal = The Journal of Biological Chemistry | volume = 283 | issue = 32 | pages = 22007–17 | date = August 2008 | pmid = 18559341 | pmc = 2494925 | doi = 10.1074/jbc.M801839200 | doi-access = free }} This enzyme catalyses the following chemical reaction:

: ATP + O-phospho-L-serine + tRNACys $\backslash rightleftharpoons$ AMP + diphosphate + O-phospho-L-seryl-tRNACys

In organisms like Archaeoglobus fulgidus, this enzyme ligates O-phosphoserine to tRNACys.