Editing Group 9 element (section)

==Biological role==
{{Main|Cobalt#Biological role}}
Of the group 9 elements, only cobalt has a biological role. It is a key constituent of [[Vitamin B12|cobalamin]], also known as vitamin B{{sub|12}}, the primary biological reservoir of cobalt as an [[ultratrace element]].<ref>{{cite book|first1=Kazuhiro|last1=Yamada|editor=Astrid Sigel |editor2=Helmut Sigel |editor3=Roland K. O. Sigel|title=Interrelations between Essential Metal Ions and Human Diseases|series=Metal Ions in Life Sciences|volume=13|date=2013|publisher=Springer|pages=295–320|chapter=Chapter 9. Cobalt: Its Role in Health and Disease|doi=10.1007/978-94-007-7500-8_9|pmid=24470095
|isbn=978-94-007-7499-5 }}</ref><ref>{{cite book|last1=Cracan|first1=Valentin |last2=Banerjee|first2=Ruma |editor1-first=Lucia |editor1-last=Banci |series=Metal Ions in Life Sciences |volume=12|chapter= Chapter 10 Cobalt and Corrinoid Transport and Biochemistry|title=Metallomics and the Cell |date=2013 |pages=333–374 |publisher=Springer |isbn=978-94-007-5560-4|doi=10.1007/978-94-007-5561-1_10|pmid=23595677 }} electronic-book {{ISBN|978-94-007-5561-1}} {{issn|1559-0836}} electronic-{{issn|1868-0402}}.
</ref> [[Bacteria]] in the stomachs of [[ruminant]] animals convert cobalt salts into vitamin B{{sub|12}}, a compound which can only be produced by bacteria or [[archaea]]. A minimal presence of cobalt in soils therefore markedly improves the health of [[grazing]] animals, and an uptake of 0.20&nbsp;mg/kg a day is recommended, because they have no other source of vitamin B{{sub|12}}.<ref>{{cite journal |last1 = Schwarz |first1 = F. J. |last2 = Kirchgessner |first2 = M. |last3 = Stangl |first3 = G. I. |title = Cobalt requirement of beef cattle – feed intake and growth at different levels of cobalt supply |journal = Journal of Animal Physiology and Animal Nutrition |volume = 83 |pages = 121–131 |date = 2000 |doi = 10.1046/j.1439-0396.2000.00258.x |issue = 3}}</ref>

Proteins based on cobalamin use [[corrin]] to hold the cobalt. Coenzyme B<sub>12</sub> features a reactive C-Co bond that participates in the reactions.<ref>{{cite book |author=Voet, Judith G. |author2=Voet, Donald |title=Biochemistry |publisher=J. Wiley & Sons |location=New York |date=1995 |page=[https://archive.org/details/biochemistry00voet_0/page/675 675] |isbn=0-471-58651-X |oclc=31819701 |url-access=registration |url=https://archive.org/details/biochemistry00voet_0/page/675 }}</ref> In humans, B<sub>12</sub> has two types of [[Alkane|alkyl]] [[ligand]]: [[Methyl group|methyl]] and adenosyl. [[Methylcobalamin|MeB<sub>12</sub>]] promotes methyl (−CH<sub>3</sub>) group transfers. The adenosyl version of B<sub>12</sub> catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. [[Methylmalonyl coenzyme A mutase]] (MUT) converts [[L-methylmalonyl-CoA|MMl-CoA]] to [[succinyl-CoA|Su-CoA]], an important step in the extraction of energy from proteins and fats.<ref>{{cite journal |last1 = Smith |first1 = David M. |last2 = Golding |first2 = Bernard T. |last3 = Radom |first3 = Leo |title = Understanding the Mechanism of B12-Dependent Methylmalonyl-CoA Mutase: Partial Proton Transfer in Action |journal = Journal of the American Chemical Society |volume = 121 |pages = 9388–9399 |date = 1999 |doi = 10.1021/ja991649a |issue = 40}}</ref>