Mapping of Selenium Metabolic Pathway in Yeast by Liquid Chromatography−Orbitrap Mass Spectrometry

Abstract

A high resolution mass spectrometric detection method is described for the identification of key metabolites in the selenium pathway in selenium enriched yeast. Iodoacetic acid (IAA) was used as the derivatizing reagent to stabilize the selenols. Oxidized forms of Selenocysteine (Se-Cys), selenohomocystine (Se-HCys), selenoglutathione (Se-GSH), seleno-γ-glutamyl-cysteine (Se-Glu-Cys), N-(2,3-dihydroxy-1-oxopropyl)-Selenocysteine (SELM-1). Selenols were also derivatized with a mercury tag, p-hydroxymercurybenzoate (PHMB). The selenol-PHMB complexes showed the overlapped isotopic patterns of selenium and mercury, which provided supporting information for the identification of selenols. Both methods showed good agreement (< 4 ppm difference) between the theoretical masses of the target compounds and the measured masses in the yeast matrix. The method using IAA as the derivatizing reagent was used to study the response of Saccharomyces cerevisiae to three forms of selenium, Se-Met, Na 2 SeO 3 (Se (IV)), and Na 2 SeO 4 ·10H 2 O (Se (VI)) (concentration of Se: 100 mg/L). The production of selenocompounds observed over a six hour period was high in the Se-Met treated group compared to the groups treated with Se (IV), Se (VI).

Cytotoxic Mechanism of Selenomethionine in Yeast

“…Indeed, the inorganic form of selenium, selenite, has been reported to be involved in induction of DNA damage (29). A sensitive method has recently been established to identify selenium compounds from yeast cells treated with SeMet, using Orbitrap mass spectrometry (30). However, metabolic changes in SeMet-treated cells were not clearly addressed in this report.…”

Recent advances in the mechanism of selenoamino acids toxicity in eukaryotic cells

“…Superoxide production was observed in SeMet-treated yeast cells and deletion of SOD1, the gene coding for superoxide dismutase, was shown to increase SeMet toxicity (113). In addition, metabolomic studies in yeast demonstrated that SeMet addition induced a redox imbalance (149,150). How exposure to SeMet generates oxidative stress remains to be established.…”

Yeast as a model system to study metabolic impact of selenium compounds

“…Selenide is also the intermediate for the formation of selenocysteine, from which selenomethionine can then be formed in organisms with a functional transsulfuration pathway. Several metabolomics studies 282930 have shown that a plethora of additional organoselenium compounds accumulate in yeast cells supplemented with selenate, selenite or selenomethionine, in addition to demonstrating that selenocysteine can also be formed from selenomethionine.…”