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|Section2= |Section3= }} Selenomethionine 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.〔P. D. Whanger, Selenocompounds in plants and animals and their biological significance, ''Journal of the American College of Nutrition'', ''21''(3), 223–232 (2002).〕 ''In vivo'', selenomethionine is randomly incorporated instead of methionine. Selenomethionine is readily oxidized.〔 E. Block, M. Birringer, W. Jiang, T. Nakahodo, H.J. Thompson, P.J. Toscano, H. Uzar, X. Zhang, and Z. Zhu, ''Allium'' chemistry: synthesis, natural occurrence, biological activity, and chemistry of ''Se''-alk(en)ylselenocysteines and their γ-glutamyl derivatives and oxidation products, ''J. Agric. Food Chem.'', ''49'', 458-470 (2001).〕 Selenomethionine's antioxidant activity arises from its ability to deplete reactive oxygen species. == Substitution chemistry issues == 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 horses causes alkali disease. 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).〔W. A. Hendrickson, Maturation of MAD phasing for the determination of macromolecular structures, ''Journal of Synchrotron Radiation'', ''6''(4), 845-851 (1999).〕 The incorporation of heavy atoms such as selenium helps solve the phase problem in X-ray crystallography.〔A. M. Larsson, Preparation and crystallization of selenomethionine protein, ''IUL Biotechnology Series, 8 (Protein Crystallization)'', 135-154 (2009).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「selenomethionine」の詳細全文を読む スポンサード リンク
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