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B6db activities: 2.9.1.2

2.9.1.2
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;
SepSecS;
SLA;
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 2.7.1.164 (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 2.9.1.1 (L-seryl-tRNA(Sec) selenium transferase).

PDB 3BC8; 3BCB; 2Z67;
Organisms -Archea -Metazoa -Human
 

Family 

2.9.1.2 (20)
 
Links Enzyme (activities) 2.9.1.2
BRENDA (activities) 2.9.1.2
KEGG (pathways) 2.9.1.2
PLPMDB (PLP mutants) 2.9.1.2
 
References
 Manhas R, Gowri VS, Madhubala R (2016) Leishmania donovani Encodes a Functional Selenocysteinyl-tRNA Synthase J Biol Chem 291 1203-20.

 Palioura S, Sherrer RL, Steitz TA, Söll D, Simonovic M. (2009) The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation Science 325 321-5.

 Araiso Y, Palioura S, Ishitani R, Sherrer RL, O'Donoghue P, Yuan J, Oshikane H, Domae N, Defranco J, Söll D, Nureki O (2008) Structural insights into RNA-dependent eukaryal and archaeal selenocysteine formation Nucleic Acids Res 36 1187-99.

 Ganichkin OM, Xu XM, Carlson BA, Mix H, Hatfield DL, Gladyshev VN, Wahl MC. (2008) Structure and catalytic mechanism of eukaryotic selenocysteine synthase J Biol Chem 283 5849-65.

 Xu, X.M.; Carlson, B.A.; Mix, H.; Zhang, Y.; Saira K.; Glass, R.S.; Berry, M.J.; Gladyshev, V.N.; Hatfield, D.L. (2007) Biosynthesis of selenocysteine on its tRNA in eukaryotes PLoS Biol. 5 e4.

 Yuan J, Palioura S, Salazar JC, Su D, O'Donoghue P, Hohn MJ, Cardoso AM, Whitman WB, Söll D. (2006) RNA-dependent conversion of phosphoserine forms selenocysteine in eukaryotes and archaea Proc Natl Acad Sci U S A 103 18923-7.

Articles on 2.9.1.2
 
last changed 2017/08/08 12:03

B6db activities