Abstract
The enzyme selenocysteine β-lyase (SCLY) was first isolated in 1982 from pig livers, followed by its identification in bacteria. SCLY works as a homodimer, utilizing pyridoxal 5’-phosphate as a cofactor, and catalyzing the specific decomposition of the amino acid selenocysteine into alanine and selenide. The enzyme is thought to deliver its selenide as a substrate for selenophosphate synthetases, which will ultimately be reutilized in selenoprotein synthesis. SCLY subcellular localization is unresolved, as it has been observed both in the cytosol and in the nucleus depending on the technical approach used. The highest SCLY expression and activity in mammals is found in the liver and kidneys. Disruption of the Scly gene in mice led to obesity, hyperinsulinemia, glucose intolerance, and hepatic steatosis, with SCLY being suggested as a participant in the regulation of energy metabolism in a sex-dependent manner. With the physiological role of SCLY still not fully understood, this review attempts to discuss the available literature regarding SCLY in animals and provides avenues for possible future investigation.
Highlights
The same research group from Kyoto University, Japan, had previously demonstrated that the amino acid selenocysteine could be synthesized in the rat liver from selenohomocysteine, sequentially utilizing the enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CGL), which usually act on the transsulfuration pathway for methionine metabolism [2]
The subcellular localization of selenocysteine β-lyase (SCLY) is still unresolved, and sorting this issue will improve our understanding of selenium metabolism and the enzyme role on it
Another unresolved issue is the particular mechanism of selenium delivery to SEPHS enzymes, as it is not currently known whether SCLY directly provides selenide to selenophosphate synthesis, or if an intermediate protein exists that receives the SCLY-produced selenide and delivers to SEPHS
Summary
Selenocysteine β-lyase Identification “We have found a novel enzyme that exclusively decomposes L-selenocysteine into L-alanine and. The above quote was the opening sentence of the abstract of a journal article in which the enzyme selenocysteine β-lyase (SCLY) was first identified and biochemically described [1]. The same research group from Kyoto University, Japan, had previously demonstrated that the amino acid selenocysteine could be synthesized in the rat liver from selenohomocysteine, sequentially utilizing the enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CGL), which usually act on the transsulfuration pathway for methionine metabolism [2]. The discovery of an enzyme, SCLY, that could decompose selenocysteine into L-alanine and selenide utilizing pyridoxal 5’-phosphate (PLP) as a required cofactor was, at the time, a notable puzzle piece in selenium metabolism and can be considered a landmark in the field. This review attempts to describe and discuss what is known about SCLY, focusing further on the eukaryotic enzyme
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