Selenomethionine
Selenomethionine (SeMet) is a naturally occurring amino acid. The L-selenomethionine enantiomer is the main form of selenium found in Brazil nuts, cereal grains, soybeans, and grassland legumes, while Se-methylselenocysteine, or its γ-glutamyl derivative, is the major form of selenium found in Astragalus, Allium, and Brassica species.<ref>Template:Cite journal</ref> In vivo, selenomethionine is randomly incorporated instead of methionine. Selenomethionine is readily oxidized.<ref>Template:Cite journal</ref>
Selenomethionine's antioxidant activity arises from its ability to deplete reactive oxygen species. Selenium and methionine also play separate roles in the formation and recycling of glutathione, a key endogenous antioxidant in many organisms, including humans.
Substitution chemistry issuesEdit
Selenium and sulfur are chalcogens that share many chemical properties so the substitution of methionine with selenomethionine may have only a limited effect on protein structure and function. However, the incorporation of selenomethionine into tissue proteins and keratin in cattle, birds, and fish causes alkali disease.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Alkali disease is characterized by emaciation, loss of hair, deformation and shedding of hooves, loss of vitality, and erosion of the joints of long bones.
Incorporation of selenomethionine into proteins in place of methionine aids the structure elucidation of proteins by X-ray crystallography using single- or multi-wavelength anomalous diffraction (SAD or MAD).<ref>Template:Cite journal</ref> The incorporation of heavy atoms such as selenium helps solve the phase problem in X-ray crystallography.<ref>Template:Cite book</ref>
Dietary intakeEdit
Selenomethionine is readily available as a dietary supplement. It has been suggested by nutritionists that selenomethionine, as an organic form of selenium, is easier for the human body to absorb than selenite, which is an inorganic form.<ref name="CL_CancerPrevention">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was determined in a clinical trial that selenomethionine is absorbed 19% better than selenite.<ref name="CL_CancerPrevention"/>
See alsoEdit
- Selenocysteine, another selenium-containing amino acid, but one that is incorporated into specific locations of specific proteins as directed by the genetic code.
- Selenoprotein
- Canadian Reference Material of selenomethionine