Editing Selenium (section)

===Evolution in biology===
{{Main|Evolution of dietary antioxidants}}

From about three billion years ago, [[prokaryotic]] selenoprotein families drove the evolution of the amino acid selenocysteine. Several selenoproteins are known in bacteria, archaea, and eukaryotes, invariably owing to the presence of selenocysteine,<ref name="glady">{{cite journal |title=Selenocysteine-containing proteins in mammals |journal=Journal of Biomedical Science |volume=6 |issue=3 |pages=151–160 |date=1999 |pmid=10343164 |doi=10.1007/BF02255899 |last1=Gladyshev |first1=Vadim N. |last2=Hatfield |first2=Dolph L.|url=https://digitalcommons.unl.edu/biochemgladyshev/77 }}</ref>  Just as for mammals, selenoprotein protect unicellular organisms against oxidative damage.

Selenoprotein families of GSH-Px and the deiodinases of eukaryotic cells seem to have a bacterial [[Phylogenetics|phylogenetic]] origin. The selenocysteine-containing form occurs in species as diverse as green algae, diatoms, sea urchins, fish, and chickens.<ref>{{cite journal |last=Stadtman |first=T. C. |title=Selenocysteine |journal=Annual Review of Biochemistry |volume=65 |pages=83–100 |date=1996 |issue=1 |pmid=8811175 |doi=10.1146/annurev.bi.65.070196.000503}}</ref>

Trace elements involved in GSH-Px and superoxide dismutase enzymes activities, i.e., selenium, [[vanadium]], [[magnesium]], [[copper]], and [[zinc]], may have been lacking in some terrestrial mineral-deficient areas.<ref name="glady" /> Marine organisms retained and sometimes expanded their selenoproteomes, whereas the selenoproteomes of some terrestrial organisms were lowered or completely lost. These findings suggest that, with the exception of [[vertebrate]]s, aquatic life supports selenium use, whereas terrestrial habitats lead to lowered use of this trace element.<ref>{{cite journal |title=Evolutionary dynamics of eukaryotic selenoproteomes: large selenoproteomes may associate with aquatic life and small with terrestrial life |journal=Genome Biology |volume=8 |issue=9 |pages=R198 |date=2007 |pmid=17880704 |pmc=2375036 |doi=10.1186/gb-2007-8-9-r198 |last1=Lobanov |first1=Alexey V. |last2=Fomenko |first2=Dmitri E. |last3=Zhang |first3=Yan |last4=Sengupta |first4=Aniruddha |last5=Hatfield |first5=Dolph L. |last6=Gladyshev |first6=Vadim N. |display-authors=3 |doi-access=free }}</ref> Marine fishes and vertebrate thyroid glands have the highest concentration of selenium and iodine. From about 500&nbsp;million years ago, freshwater and terrestrial plants slowly optimized the production of "new" endogenous antioxidants such as [[ascorbic acid]] (vitamin C), [[polyphenol]]s (including flavonoids), [[tocopherol]]s, etc. A few of these appeared in the last 50–200 million years in fruits and flowers of [[angiosperm]] plants. In fact, the angiosperms (the dominant type of plant today) and most of their antioxidant pigments evolved during the late [[Jurassic]] period.{{Citation needed|date=June 2016}}

About 200 million years ago, new selenoproteins were developed as mammalian GSH-Px enzymes.<ref>{{cite journal |title=Reconsidering the evolution of eukaryotic selenoproteins: a novel nonmammalian family with scattered phylogenetic distribution |journal=EMBO Reports |volume=5 |issue=1 |pages=71–7 |date=2004 |pmid=14710190 |pmc=1298953 |doi=10.1038/sj.embor.7400036 |last1=Castellano |first1=Sergi |last2=Novoselov |first2=Sergey V. |last3=Kryukov |first3=Gregory V. |last4=Lescure |first4=Alain |last5=Blanco |first5=Enrique |last6=Krol |first6=Alain |last7=Gladyshev |first7=Vadim N. |last8=Guigó |first8=Roderic |display-authors=3}}</ref><ref>{{cite journal |title=The prokaryotic selenoproteome |journal=EMBO Reports |volume=5 |issue=5 |pages=538–43 |date=2004 |pmid=15105824 |pmc=1299047 |doi=10.1038/sj.embor.7400126 |last1=Kryukov |first1=Gregory V. |last2=Gladyshev |first2=Vadim N.}}</ref><ref>{{cite journal |title=Selenoprotein synthesis in archaea: identification of an mRNA element of ''Methanococcus jannaschii'' probably directing selenocysteine insertion |journal=Journal of Molecular Biology |volume=266 |issue=4 |pages=637–41 |date=1997 |pmid=9102456 |doi=10.1006/jmbi.1996.0812 |last1=Wilting |first1=R. |last2=Schorling |first2=S. |last3=Persson |first3=B. C. |last4=Böck |first4=A.}}</ref><ref>{{cite journal |title=The microbial selenoproteome of the Sargasso Sea |journal=Genome Biology |volume=6 |issue=4 |pages=R37 |date=2005 |pmid=15833124 |pmc=1088965 |doi=10.1186/gb-2005-6-4-r37 |last1=Zhang |first1=Yan |last2=Fomenko |first2=Dmitri E. |last3=Gladyshev |first3=Vadim N. |doi-access=free }}</ref>