Recent developments in selenium metabolism and chemical speciation: a review

Area of Science:

• Biochemistry
• Molecular Biology
• Nutritional Science

Background:

• Selenium's biological roles, including antioxidant properties and regulation of thyroid hormone metabolism, cell growth, and eicosanoid biosynthesis, are increasingly understood.
• Selenoprotein synthesis uniquely utilizes the UGA stop codon for selenocysteine insertion, requiring specific gene products and mRNA structures.

Purpose of the Study:

• To elucidate the biochemical mechanisms and biological functions of selenium.
• To highlight the unique aspects of selenoprotein synthesis and selenium's role in enzyme activity.
• To explore the bioavailability of different selenium forms and the potential for identifying selenium status markers.

Main Methods:

• Review of current literature on selenium biochemistry and biological functions.
• Analysis of the mechanism of selenocysteine insertion via UGA codon reassignment.
• Discussion of selenium's redox activity in selenoproteins and the impact of cysteine substitution.
• Evaluation of selenium bioavailability from organic and inorganic sources.

Main Results:

• Selenium's primary functions are linked to its antioxidant capacity and roles in thyroid hormone metabolism, cell growth, and eicosanoid synthesis.
• Selenocysteine insertion into proteins is directed by the UGA codon, dependent on specific cellular machinery.
• Selenoproteins exhibit redox activity crucial for their function, with cysteine substitution leading to loss of activity.
• Selenoamino acids offer the highest bioavailability among selenium forms.

Conclusions:

• Selenium's biological significance is primarily mediated by its incorporation into selenoproteins, where its redox properties are essential.
• Understanding selenium biochemistry and developing methods to study its distribution are key to identifying biomarkers for selenium status in various health conditions.