Editing Vanadium (section)

== Biological role ==
Vanadium has a more significant role in marine environments than terrestrial ones.<ref>{{cite book |title=Vanadium and Its Role in Life |publisher=CRC |year=1995 |isbn=978-0-8247-9383-8 |editor1-last=Sigel |editor1-first=Astrid |series=Metal Ions in Biological Systems |volume=31 |editor2-last=Sigel |editor2-first=Helmut}}</ref>
[[File:Bluebell tunicates Nick Hobgood.jpg|thumb|[[Tunicate]]s such as this bluebell tunicate contain vanadium as [[vanabins]].]]
[[File:Amanita muscaria 3 vliegenzwammen op rij.jpg|thumb|''[[Amanita muscaria]]'' contains [[amavadin]].]]

=== Vanadoenzymes ===
Several species of marine [[algae]] produce [[vanadium bromoperoxidase]] as well as the closely related [[chloroperoxidase]] (which may use a [[heme]] or vanadium cofactor) and [[iodoperoxidase]]s. The bromoperoxidase produces an estimated 1–2 million tons of [[bromoform]] and 56,000 tons of [[bromomethane]] annually.<ref>{{cite journal |last1=Gribble |first1=Gordon W. |date=1999 |title=The diversity of naturally occurring organobromine compounds |journal=Chemical Society Reviews |volume=28 |issue=5 |pages=335–346 |doi=10.1039/a900201d}}</ref> Most naturally occurring [[organobromine compound]]s are produced by this enzyme,<ref>{{cite journal |last1=Butler |first1=Alison |last2=Carter-Franklin |first2=Jayme N. |date=2004 |title=The role of vanadium bromoperoxidase in the biosynthesis of halogenated marine natural products |journal=Natural Product Reports |volume=21 |issue=1 |pages=180–188 |doi=10.1039/b302337k |pmid=15039842}}</ref> catalyzing the following reaction (R-H is hydrocarbon substrate):

{{block indent|R-H + Br<sup>−</sup> + H<sub>2</sub>O<sub>2</sub> → R-Br + H<sub>2</sub>O + OH<sup>−</sup>}}

A [[vanadium nitrogenase]] is used by some [[nitrogen fixation|nitrogen-fixing]] micro-organisms, such as ''[[Azotobacter]]''. In this role, vanadium serves in place of the more common [[molybdenum]] or [[iron]], and gives the [[nitrogenase]] slightly different properties.<ref>{{cite journal |last1=Robson |first1=R. L. |last2=Eady |first2=R. R. |last3=Richardson |first3=T. H. |last4=Miller |first4=R. W. |last5=Hawkins |first5=M. |last6=Postgate |first6=J. R. |date=1986 |title=The alternative nitrogenase of Azotobacter chroococcum is a vanadium enzyme |journal=Nature |volume=322 |issue=6077 |pages=388–390 |bibcode=1986Natur.322..388R |doi=10.1038/322388a0 |s2cid=4368841}}</ref>

=== Vanadium accumulation in tunicates ===
Vanadium is essential to [[tunicate]]s, where it is stored in the highly acidified [[vacuole]]s of certain blood cell types, designated [[vanadocyte]]s. [[Vanabins]] (vanadium-binding proteins) have been identified in the cytoplasm of such cells. The concentration of vanadium in the blood of [[Ascidiacea|ascidian]] tunicates is as much as ten million times higher{{specify|date=April 2014}}<ref>{{cite journal |last1=Smith |first1=M. J. |date=1989 |title=Vanadium biochemistry: The unknown role of vanadium-containing cells in ascidians (sea squirts) |journal=Experientia |volume=45 |issue=5 |pages=452–7 |doi=10.1007/BF01952027 |pmid=2656286 |s2cid=43534732}}</ref><ref>{{cite journal |last1=MacAra |first1=Ian G. |last2=McLeod |first2=G. C. |last3=Kustin |first3=Kenneth |date=1979 |title=Tunichromes and metal ion accumulation in tunicate blood cells |journal=Comparative Biochemistry and Physiology B |volume=63 |issue=3 |pages=299–302 |doi=10.1016/0305-0491(79)90252-9}}</ref> than the surrounding seawater, which normally contains 1 to 2&nbsp;μg/L.<ref>{{cite journal |last1=Trefry |first1=John H. |last2=Metz |first2=Simone |date=1989 |title=Role of hydrothermal precipitates in the geochemical cycling of vanadium |journal=Nature |volume=342 |issue=6249 |pages=531–533 |bibcode=1989Natur.342..531T |doi=10.1038/342531a0 |s2cid=4351410}}</ref><ref>{{cite journal |last1=Weiss |first1=H. |last2=Guttman |first2=M. A. |last3=Korkisch |first3=J. |last4=Steffan |first4=I. |date=1977 |title=Comparison of methods for the determination of vanadium in sea-water |journal=Talanta |volume=24 |issue=8 |pages=509–11 |doi=10.1016/0039-9140(77)80035-0 |pmid=18962130}}</ref> The function of this vanadium concentration system and these vanadium-bearing proteins is still unknown, but the vanadocytes are later deposited just under the outer surface of the tunic, where they may deter [[predation]].<ref>{{cite book |last1=Ruppert |first1=Edward E. |title=Invertebrate Zoology |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |date=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |edition=7th |pages=947}}</ref>

=== Fungi ===
''[[Amanita muscaria]]'' and related species of macrofungi accumulate vanadium (up to 500&nbsp;mg/kg in dry weight). Vanadium is present in the [[coordination complex]] [[amavadin]]<ref>{{cite journal |last1=Kneifel |first1=Helmut |last2=Bayer |first2=Ernst |date=June 1973 |title=Determination of the Structure of the Vanadium Compound, Amavadine, from Fly Agaric |journal=Angewandte Chemie International Edition in English |volume=12 |issue=6 |pages=508 |doi=10.1002/anie.197305081}}</ref> in fungal fruit-bodies. The biological importance of the accumulation is unknown.<ref>{{cite journal |last1=Falandysz |first1=J. |last2=Kunito |first2=T. |last3=Kubota |first3=R. |last4=Lipka |first4=K. |last5=Mazur |first5=A. |last6=Falandysz |first6=Justyna J. |last7=Tanabe |first7=S. |date=31 August 2007 |title=Selected elements in fly agaric Amanita muscaria |journal=Journal of Environmental Science and Health, Part A |volume=42 |issue=11 |pages=1615–1623 |doi=10.1080/10934520701517853 |pmid=17849303 |bibcode=2007JESHA..42.1615F |s2cid=26185534}}</ref><ref>{{cite journal |last1=Berry |first1=Robert E. |last2=Armstrong |first2=Elaine M. |last3=Beddoes |first3=Roy L. |last4=Collison |first4=David |last5=Ertok |first5=S. Nigar |last6=Helliwell |first6=Madeleine |last7=Garner |first7=C. David |date=15 March 1999 |title=The Structural Characterization of Amavadin |journal=Angewandte Chemie |volume=38 |issue=6 |pages=795–797 |doi=10.1002/(SICI)1521-3773(19990315)38:6<795::AID-ANIE795>3.0.CO;2-7 |pmid=29711812|doi-access=free }}</ref> Toxic or [[peroxidase]] enzyme functions have been suggested.<ref name="da Silva Fraústo 2013">{{cite journal |last1=da Silva |first1=José A.L. |last2=Fraústo da Silva |first2=João J.R. |last3=Pombeiro |first3=Armando J.L. |date=August 2013 |title=Amavadin, a vanadium natural complex: Its role and applications |journal=Coordination Chemistry Reviews |volume=257 |issue=15–16 |pages=2388–2400 |doi=10.1016/j.ccr.2013.03.010}}</ref>

=== Mammals ===
Deficiencies in vanadium result in reduced growth in rats.<ref>{{cite journal |last1=Schwarz |first1=Klaus |last2=Milne |first2=David B. |date=22 October 1971 |title=Growth Effects of Vanadium in the Rat |journal=Science |volume=174 |issue=4007 |pages=426–428 |bibcode=1971Sci...174..426S |doi=10.1126/science.174.4007.426 |pmid=5112000 |s2cid=24362265}}</ref> The U.S. Institute of Medicine has not confirmed that vanadium is an essential nutrient for humans, so neither a Recommended Dietary Intake nor an Adequate Intake have been established. Dietary intake is estimated at 6 to 18&nbsp;μg/day, with less than 5% absorbed. The [[tolerable upper intake level|Tolerable Upper Intake Level]] (UL) of dietary vanadium, beyond which adverse effects may occur, is set at 1.8&nbsp;mg/day.<ref>Nickel. IN: [https://www.nap.edu/read/10026/chapter/15 Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Copper] {{Webarchive|url=https://web.archive.org/web/20170922174144/https://www.nap.edu/read/10026/chapter/15|date=22 September 2017}}. National Academy Press. 2001, PP. 532–543.</ref>

=== Research ===
[[Vanadyl sulfate]] as a dietary supplement has been researched as a means of increasing insulin sensitivity or otherwise improving glycemic control in people who are diabetic. Some of the trials had significant treatment effects but were deemed as being of poor study quality. The amounts of vanadium used in these trials (30 to 150&nbsp;mg) far exceeded the safe upper limit.<ref name="Smith2008">{{cite journal |last1=Smith |first1=D.M. |last2=Pickering |first2=R.M. |last3=Lewith |first3=G.T. |date=31 January 2008 |title=A systematic review of vanadium oral supplements for glycaemic control in type 2 diabetes mellitus |journal=QJM |volume=101 |issue=5 |pages=351–358 |doi=10.1093/qjmed/hcn003 |pmid=18319296}}</ref><ref>{{cite journal |year=2009 |title=Vanadium (vanadyl sulfate). Monograph |journal=Altern Med Rev |volume=14 |issue=2 |pages=177–80 |pmid=19594227}}</ref> The conclusion of the systemic review was "There is no rigorous evidence that oral vanadium supplementation improves glycaemic control in type 2 diabetes. The routine use of vanadium for this purpose cannot be recommended."<ref name="Smith2008" />

In [[astrobiology]], it has been suggested that discrete vanadium accumulations on [[Mars]] could be a potential microbial [[biosignature]] when used in conjunction with [[Raman spectroscopy]] and morphology.<ref name="Biosignature Vanadium">{{cite news |last=Lynch |first=Brendan M. |date=21 September 2017 |title=Hope to discover sure signs of life on Mars? New research says look for the element vanadium |work=PhysOrg |url=https://phys.org/news/2017-09-life-mars-element-vanadium.html |url-status=live |access-date=2017-10-14 |archive-url=https://web.archive.org/web/20211011173212/https://phys.org/news/2017-09-life-mars-element-vanadium.html |archive-date=11 October 2021}}</ref><ref name="Vanadium Craig">{{cite journal |last1=Marshall |first1=C. P |last2=Olcott Marshall |first2=A |last3=Aitken |first3=J. B |last4=Lai |first4=B |last5=Vogt |first5=S |last6=Breuer |first6=P |last7=Steemans |first7=P |last8=Lay |first8=P. A |year=2017 |title=Imaging of Vanadium in Microfossils: A New Potential Biosignature |journal=Astrobiology |volume=17 |issue=11 |pages=1069–1076 |bibcode=2017AsBio..17.1069M |doi=10.1089/ast.2017.1709 |osti=1436103 |pmid=28910135}}</ref>