Selenocysteine lyase
In enzymology, a selenocysteine lyase (SCL) (EC 4.4.1.16) is an enzyme that catalyzes the chemical reaction
- L-selenocysteine + reduced acceptor selenide + L-alanine + acceptor
| selenocysteine lyase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC number | 4.4.1.16 | ||||||||
| CAS number | 82047-76-5 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
Thus, the two substrates of this enzyme are L-selenocysteine and reduced acceptor, whereas its 3 products are selenide, L-alanine, and acceptor. This enzyme employs one cofactor, pyridoxal phosphate.
Nomenclature
This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is L-selenocysteine selenide-lyase (L-alanine-forming). Other names in common use include selenocysteine reductase, and selenocysteine beta-lyase.
Function
This enzyme participates in selenoamino acid metabolism by recycling Se from selenocysteine during the degradation of selenoproteins, providing an alternate source of Se for selenocysteine biosynthesis.[1]
Structure and mechanism
Mammalian SCL forms a homodimer while bacterial SCL is monomeric. In mammals, highest SCL activity is found in the liver and kidney.[1][2]
While selenocysteine lyases generally catalyze the removal of both selenium or sulfur from selenocysteine or cysteine, respectively, human selenocysteine lyases are specific for selenocysteine. Asp146 has been identified as the key residue that preserves specificity in human SCL.[3]
References
- Labunskyy VM, Hatfield DL, Gladyshev VN (July 2014). "Selenoproteins: molecular pathways and physiological roles". Physiological Reviews. 94 (3): 739–77. doi:10.1152/physrev.00039.2013. PMC 4101630. PMID 24987004.
- Mihara H, Kurihara T, Watanabe T, Yoshimura T, Esaki N (March 2000). "cDNA cloning, purification, and characterization of mouse liver selenocysteine lyase. Candidate for selenium delivery protein in selenoprotein synthesis". The Journal of Biological Chemistry. 275 (9): 6195–200. doi:10.1074/jbc.275.9.6195. PMID 10692412.
- Collins R, Johansson AL, Karlberg T, Markova N, van den Berg S, Olesen K, Hammarström M, Flores A, Schüler H, Schiavone LH, Brzezinski P, Arnér ES, Högbom M (2012). "Biochemical discrimination between selenium and sulfur 1: a single residue provides selenium specificity to human selenocysteine lyase". PLOS ONE. 7 (1): e30581. Bibcode:2012PLoSO...730581C. doi:10.1371/journal.pone.0030581. PMC 3266270. PMID 22295093.
Further reading