Chemical synthesis and diselenide metathesis in selenocysteine- containing peptides

Abstract

Selenoproteins, the functional form of the essential trace element selenium, play a vital role in maintaining redox homeostasis in humans. Selenocysteine (Sec), which constitutes the active center of many selenoproteins, is introduced to the polypeptide chain by a unique biosynthetic insertion mechanism, making the expression of selenoproteins through biological means challenging. Compared to its analogue cysteine (Cys), Sec exhibits a lower redox potential, facilitating the oxidation of selenol groups to form diselenide bonds. These diselenide bonds are more resistant to reduction than disulfide bonds, providing an enhanced stability to peptides under reducing conditions. On the other hand, due to the larger atomic radius of selenium, the dissociation energy of the diselenide bond is lower than that of the disulfide bond, rendering them more prone to diselenide metathesis. This mini-review summarizes the use of Sec for the chemical synthesis of proteins, Sec-containing peptides and the selenoproteins. The diselenide metathesis reaction of Sec-containing peptides is also reviewed.

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