To use all functions of this page, please activate cookies in your browser.
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
Additional recommended knowledge
Corphin in context
Nature uses many tetrapyrroles - hemes, chlorophyll, and vitamin B12. F430 is the most reduced tetrapyrrole in nature with only five double bonds. This particular tetrapyrrole derivative is called a corphin. Because of its relative lack of conjugated unsaturation, it is yellow, not the intense purple-red associated with more unsaturated tetrapyrroles. It is also the only tetrapyrrole derivative found in nature to contain nickel. Ni(II) is too small for the N4 binding site of the corphin, which causes the macrocycle to adopt a ruffled structure.
Proposed mechanism of methanogenesis
The active form of F430 contains Ni(I), analogously to the reduced B12 cofactors that feature Co(I). Whereas Co(I) is d8 and diamagnetic, Ni(I) is d9 and paramagnetic. The mechanism by which Nature cleaves the CH3-S bond in methyl coenzyme M is presently (2006) unclear although it is known that both coenzyme M and coenzyme B fits into a channel terminated by the axial site on nickel. A plausible mechanism entails electron transfer from Ni(I) (to give Ni(II)), and this electron transfer initiates formation of CH4. Coupling of the coenzyme M thiyl radical with HS coenzyme B releases a proton and re-reduces Ni(II) by one-electron, regenerating Ni(I).
Anaerobic methane oxidation
F430 occurs in very high concentrations in bacteria that are thought to be involved in reverse methanogenesis, where methane is converted to methyl coenzyme M. Organisms that promote this remarkable reaction contain 7% by weight nickel protein.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "F430". A list of authors is available in Wikipedia.|