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Description O-phospho-L-seryl-tRNA(Sec):L-selenocysteinyl-tRNA synthase
Alternative names L-phosphoseryl-tRNA(Ser):selenophosphate seleniumtransferase;
Sep (O-phosphoserine) tRNA:Sec (selenocysteine) tRNA synthase;
Sec synthase (ambiguous).
Catalyzed reaction O-phosphoseryl-tRNA(Sec) + Selenophosphate = L-Selenocysteinyl-tRNA(Sec) + Orthophosphate
Cofactor Pyridoxal phosphate
Comments A pyridoxal-phosphate protein. In archaea and eukarya selenocysteine formation is achieved by a two-step process: EC (O-phosphoseryl-tRNASec kinase) phosphorylates the endogenous L-seryl-tRNASec to O-phospho-L-seryl-tRNASec, and then this misacylated amino acid-tRNA species is converted to L-selenocysteinyl-tRNASec by Sep-tRNA:Sec-tRNA synthase.
This activity is specific of archaea and eukaryotes; these organisms synthesize L-selenocysteinyl-tRNA(Sec) from L-seryl-tRNA(Sec)trough a two-step pathway.
First, O-phosphoseryl-tRNA(Sec) kinase (PSTK) converts Ser-tRNA(Sec) to O-phosphoseryl-tRNA(Ser). This compound is then used as the substrate for Sep-tRNA:Sec-tRNA synthase (SepSecS).

In bacteria, L-seryl-tRNA(Sec) is directly converted to L-selenocysteinyl-tRNA(Sec) by EC (L-seryl-tRNA(Sec) selenium transferase).

PDB 3BC8; 3BCB; 2Z67;
Organisms -Archea -Metazoa -Human
Links Enzyme (activities)
BRENDA (activities)
KEGG (pathways)
PLPMDB (PLP mutants)
References Articles on
last changed 2017/08/08 12:03

B6db activities