Identification of Selenoproteins Formed via Biotransformation of Selenium-enriched Streptomyces platensis and Their Oxygen Free Radical Scavenging Activities
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Abstract:
Selenium (Se) content and distribution of Se-containing biotransformation proteins (SeP) in Se-enriched Streptomyces platensis (SeSP) were explored. Additionally, the in vitro scavenging activity of oxygen free radicals by SeP was studied. Total proteins (TP) in S. platensis were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Se content in different molecular-weight proteins was measured using inductively-coupled plasma mass spectrometry (ICP-MS). Laser ablation (LA)-ICP-MS was used for in situ detection of Se content in purified Se phycocyanin (SePC) within the electrophoresis gel. The in vitro clearance of superoxide and hydroxyl free radicals by SeP was investigated by chemiluminescence. The results showed that Se content in SeSP-TP was 32-fold higher than that in non-enriched S. platensis (SP), reaching 805.48 μg/g, while 75.81% oftotal Se was distributed in low-molecular weight SePs (LMWSeP), with molecular weights ≤ 25 ku. LA-ICP-MS results confirmed that purified SePC subunits contained stable, covalently-bound, active Se. The maximum clearance rate of free radicals by LMWSeP was over 70%. The findings suggest that SeSP cultures could be used to produce active SeP by biotransformation. The LMWSeP components in SeSPs are a source of natural Se with high anti-oxidation activity. Further studies are required to determine the form of Se, transformation mechanism, and in vivo bioactivity.
