A Comprehensive Analysis of Selenium-Binding Proteins in the Brain Using Its Reactive Metabolite.

In this chapter, the speciation analysis of the fish-specific selenoproteins and low molecular mass organoselenium compounds from fish was described. Selenium is essential to fish as well as mammals. The selenoproteomes (sets of seleno-L-cysteine (SeCys)-containing proteins) of fish are greater in number than those of mammals (25 selenoproteins in humans); at 41 selenoproteins, the selenoproteomes of fish are among the largest known. Fish have several species-specific selenoproteins (fish 15 kDa selenoprotein-like protein, selenoprotein J and selenoprotein L). Many low-mass organoselenium species are detected in fish samples other than seleno-L-methionine and SeCys derivatives. Although the selenium contents in fish are higher than in terrestrial foodstuffs, little is known about the chemical forms of such organoselenium species in fish. Fish appear to contain nutritionally effective organoselenium compounds that have not yet been chemically identified.