:Cofactor F430
{{distinguish|Coenzyme F420}}
{{chembox
| ImageFile=Coenzyme F430.svg
| ImageSize=220px
| IUPACName=
| OtherNames=
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct}}
| CASNo= 73145-13-8
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 21864910
| PubChem=5460020
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 28265
| SMILES= CC12CC(=O)NC13CC4C(C(C(=N4)CC5C(C6CCC(=O)C(=C7C(C(C(=CC(=N3)C2CCC(=O)O)[N-]7)CC(=O)O)CCC(=O)O)C6=N5)CC(=O)O)(C)CC(=O)N)CCC(=O)O.[Ni]
| InChI = InChI=1S/C42H52N6O13.Ni/c1-40(16-30(43)50)22(5-9-33(54)55)27-15-42-41(2,17-31(51)48-42)23(6-10-34(56)57)26(47-42)13-24-20(11-35(58)59)19(4-8-32(52)53)39(45-24)37-28(49)7-3-18-21(12-36(60)61)25(46-38(18)37)14-29(40)44-27;/h13,18-23,25,27H,3-12,14-17H2,1-2H3,(H9,43,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61);/p-1/t18-,19-,20-,21-,22+,23+,25+,27-,40-,41-,42-;/m0./s1
| InChIKey = QFGKGCZCUVIENT-SXMZNAGASA-M
}}
|Section2={{Chembox Properties
| Formula={{chem|C|42|H|51|N|6|NiO|13|−}}
| MolarMass=906.58014
| Appearance=Yellow solid
| Density=
| MeltingPt=
| BoilingPt=
| Solubility=
}}
|Section3={{Chembox Hazards
| MainHazards=
| FlashPt=
| AutoignitionPt =
}}
}}
F430 is the cofactor (sometimes called the coenzyme) of the enzyme methyl coenzyme M reductase (MCR).{{cite book | first1=Ragdale | last1= Stephen W. | chapter= Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis and the First Step in Anaerobic Oxidation of the Greenhouse Gas Methane | editor=Peter M.H. Kroneck and Martha E. Sosa Torres | title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment | series=Metal Ions in Life Sciences | volume=14 | year=2014 | publisher=Springer | pages=125–145 | doi=10.1007/978-94-017-9269-1_6 | pmid= 25416393 | isbn= 978-94-017-9268-4 }}{{cite journal |doi=10.1038/nrmicro.2016.170 |title=Masters of methane |year=2016 |last1=Hofer |first1=Ursula |journal=Nature Reviews Microbiology |volume=14 |issue=12 |pages=727 |pmid=27818502 |s2cid=35175663 |doi-access=free }}
MCR catalyzes the reaction {{EC number |2.8.4.1}} that releases methane in the final step of methanogenesis:
:{{chem|link=coenzyme M|CH|3|–S–CoM}} + HS–CoB → {{chem|CH|4}} + CoB–S–S–CoM
| File:Coenzyme M (CoM).svg |
It is found only in methanogenic Archaea{{cite journal | doi=10.1099/00221287-144-9-2377 | author=Thauer RK | title=Biochemistry of Methanogenesis: a Tribute to Marjory Stephenson | journal=Microbiology | year=1998 | volume=144 | issue=9 | pages=2377–2406 | pmid=9782487 | doi-access=free }} and anaerobic methanotrophic Archaea. It occurs in relatively high concentrations in archaea that are involved in reverse methanogenesis: these can contain up to 7% by weight of the nickel protein.{{cite journal |vauthors=Krüger M, Meyerdierks A, Glöckner FO |title=A conspicuous nickel protein in microbial mats that oxidize methane anaerobically |journal=Nature |volume=426 |issue=6968 |pages=878–81 |date=December 2003 |pmid=14685246 |doi=10.1038/nature02207 |display-authors=etal|bibcode=2003Natur.426..878K |s2cid=4383740 }}
Structure
The trivial name cofactor F430 was assigned in 1978 based on the properties of a yellow sample extracted from Methanobacterium thermoautotrophicum, which had a spectroscopic maximum at 430 nm.{{cite journal |doi=10.1111/j.1574-6968.1978.tb01916.x |title=Chromophoric factors F342 and F430 of Methanobacterium thermoautotrophicum |year=1978 |last1=Gunsalus |first1=R.P. |last2=Wolfe |first2=R.S. |journal=FEMS Microbiology Letters |volume=3 |issue=4 |pages=191–193 |doi-access=free }} It was identified as the MCR cofactor in 1982{{cite journal |doi=10.1073/pnas.79.12.3707 |title=Nickel-containing factor F430: Chromophore of the methylreductase of Methanobacterium |year=1982 |last1=Ellefson |first1=W. L. |last2=Whitman |first2=W. B. |last3=Wolfe |first3=R. S. |journal=Proceedings of the National Academy of Sciences |volume=79 |issue=12 |pages=3707–3710 |pmid=6954513 |pmc=346495 |bibcode=1982PNAS...79.3707E |doi-access=free }} and the complete structure was deduced by X-ray crystallography and NMR spectroscopy.{{cite journal |vauthors=Färber G, Keller W, Kratky C, Jaun B, Pfaltz A, Spinner C, Kobelt A, Eschenmoser A |title=Coenzyme F430 from Methanogenic Bacteria : Complete Assignment of Configuration Based on an X-ray Analysis of 12,13-diepi-F430 Pentamethyl Ester and on NMR Spectroscopy |journal=Helvetica Chimica Acta |volume=74 |issue=4 |pages=697–716 |year=1991 |doi=10.1002/hlca.19910740404}} Coenzyme F430 features a reduced porphyrin in a macrocyclic ring system called a corphin.{{cite journal |doi=10.1111/j.1749-6632.1986.tb48030.x |year=1986 |volume=471 |issue=1 International |last1=Eschenmoser |first1=A. |title=Chemistry of Corphinoids |journal=Annals of the New York Academy of Sciences |pages=108–129 |bibcode=1986NYASA.471..108E |s2cid=83719424 }} In addition, it possesses two additional rings in comparison to the standard tetrapyrrole (rings A-D), having a γ-lactam ring E and a keto-containing carbocyclic ring F. It is the only natural tetrapyrrole containing nickel, an element rarely found in biological systems.{{cite book |isbn=9781119159834 |title=Metalloprotein Active Site Assembly |last1=Johnson |first1=Michael K. |last2=Scott |first2=Robert A. |date=2 October 2017 |publisher=Wiley }}
Biosynthesis
| File:Uroporphyrinogen III skeletal.svg |
The biosynthesis builds from uroporphyrinogen III, the progenitor of all natural tetrapyrroles, including chlorophyll, vitamin B12, phycobilins, siroheme, heme, and heme d1. It is converted to sirohydrochlorin via dihydrosirohydrochlorin.{{Cite journal|last1=Mucha|first1=Helmut|last2=Keller|first2=Eberhard|last3=Weber|first3=Hans|last4=Lingens|first4=Franz|last5=Trösch|first5=Walter|date=1985-10-07|title=Sirohydrochlorin, a precursor of factor F430 biosynthesis in Methanobacterium thermoautotrophicum|journal=FEBS Letters|volume=190|issue=1|pages=169–171|doi=10.1016/0014-5793(85)80451-8|doi-access=free|bibcode=1985FEBSL.190..169M }} Insertion of nickel into this tetrapyrrole is catalysed in reaction {{EC number|4.99.1.11}} by the same chelatase, CbiX, which inserts cobalt in the biosynthesis of cobalamin, here giving nickel(II)-sirohydrochlorin.{{cite journal |doi=10.1038/nature21427 |year=2017 |volume=543 |issue=7643 |last1=Moore |first1=Simon J. |last2=Sowa |first2=Sven T. |last3=Schuchardt |first3=Christopher |last4=Deery |first4=Evelyne |last5=Lawrence |first5=Andrew D. |last6=Ramos |first6=José Vazquez |last7=Billig |first7=Susan |last8=Birkemeyer |first8=Claudia |last9=Chivers |first9=Peter T. |last10=Howard |first10=Mark J. |last11=Rigby |first11=Stephen E. J. |last12=Layer |first12=Gunhild |last13=Warren |first13=Martin J. |title=Elucidation of the biosynthesis of the methane catalyst coenzyme F430 |journal=Nature |pages=78–82 |pmid=28225763 |pmc=5337119 |bibcode=2017Natur.543...78M }}
File:Biosynthesis of seco Cofactor F430.svg
The ATP-dependent Ni-sirohydrochlorin a,c-diamide synthase (CfbE) then converts the a and c acetate side chains to acetamide in reactions {{EC number |6.3.5.12}}, generating nickel(II)-sirohydrochlorin a,c-diamide. The sequence of the two amidations is random. A two-component complex Ni-sirohydrochlorin a,c-diamide reductive cyclase (CfbCD) carries out a 6-electron and 7-proton reduction of the ring system in a reaction {{EC number |6.3.3.7}} generating the 15,173-seco-F430-173-acid (seco-F430) intermediate. Reduction involves ATP hydrolysis and electrons are relayed through two 4Fe-4S centres. In the final step, the keto-containing carbocyclic ring F is formed by an ATP-dependent enzyme Coenzyme F(430) synthetase (CfbB) in reaction {{EC number |6.4.1.9}}, generating coenzyme F430.{{cite journal |doi=10.1126/science.aag2947 |doi-access=free |title=The biosynthetic pathway of coenzyme F430 in methanogenic and methanotrophic archaea |year=2016 |last1=Zheng |first1=Kaiyuan |last2=Ngo |first2=Phong D. |last3=Owens |first3=Victoria L. |last4=Yang |first4=Xue-Peng |last5=Mansoorabadi |first5=Steven O. |journal=Science |volume=354 |issue=6310 |pages=339–342 |pmid=27846569 |bibcode=2016Sci...354..339Z }}{{cite web |url=https://biocyc.org/META/NEW-IMAGE?type=PATHWAY&object=PWY-5196|title=Pathway: factor 430 biosynthesis |author=R. Caspi |publisher=MetaCyc Metabolic Pathway Database |date=2017-01-09 |access-date=2020-04-27 }} This enzyme is a MurF-like ligase, as found in peptidoglycan biosynthesis.
References
{{Reflist}}
{{tetrapyrroles}}
{{Enzyme cofactors}}