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3D model (JSmol)
  • InChI=1S/C42H46N4O16/c1-41(17-39(59)60)23(5-9-35(51)52)29-14-27-21(11-37(55)56)19(3-7-33(47)48)25(43-27)13-26-20(4-8-34(49)50)22(12-38(57)58)28(44-26)15-31-42(2,18-40(61)62)24(6-10-36(53)54)30(46-31)16-32(41)45-29/h13-16,23-24,43-44H,3-12,17-18H2,1-2H3,(H,47,48)(H,49,50)(H,51,52)(H,53,54)(H,55,56)(H,57,58)(H,59,60)(H,61,62)/t23-,24-,41+,42+/m1/s1
  • C[C@@]1([C@@H](C2=NC1=CC3=NC(=CC4=C(C(=C(N4)C=C5C(=C(C(=C2)N5)CC(=O)O)CCC(=O)O)CCC(=O)O)CC(=O)O)[C@@]([C@@H]3CCC(=O)O)(C)CC(=O)O)CCC(=O)O)CC(=O)O
Appearance yellow solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Sirohydrochlorin is a tetrapyrrole macrocyclic metabolic intermediate in the biosynthesis of sirohaem, the iron-containing prosthetic group in sulfite reductase enzymes. It is also the biosynthetic precursor to cofactor F430, an enzyme which catalyzes the release of methane in the final step of methanogenesis.[1]


Sirohydrochlorin was first isolated in the early 1970s when it was shown to be the metal-free form of the prosthetic group in the ferredoxin-nitrite reductase from spinach.[2] Its chemical identity was established by spectroscopy and by total synthesis.[3][4][5]


Sirohydrochlorin is derived from a tetrapyrrolic structural framework created by the enzymes deaminase and cosynthetase which transform aminolevulinic acid via porphobilinogen and hydroxymethylbilane to uroporphyrinogen III. The latter is the first macrocyclic intermediate common to haem, chlorophyll, sirohaem and vitamin B12. Uroporphyrinogen III is subsequently transformed by the addition of two methyl groups to form dihydrosirohydrochlorin and this is oxidised to give sirohydrochlorin.[6]

See also[edit]


  1. ^ Mucha, Helmut; Keller, Eberhard; Weber, Hans; Lingens, Franz; Trösch, Walter (1985-10-07). "Sirohydrochlorin, a precursor of factor F430 biosynthesis in Methanobacterium thermoautotrophicum". FEBS Letters. 190 (1): 169–171. doi:10.1016/0014-5793(85)80451-8.
  2. ^ Murphy, M. J.; Siegel, L. M.; Tove, S. R.; Kamin, H. (1974). "Siroheme: A New Prosthetic Group Participating in Six-Electron Reduction Reactions Catalyzed by Both Sulfite and Nitrite Reductases". Proceedings of the National Academy of Sciences. 71 (3): 612–616. Bibcode:1974PNAS...71..612M. doi:10.1073/pnas.71.3.612. PMC 388061. PMID 4595566.
  3. ^ Scott, A. Ian; Irwin, Anthony J.; Siegel, Lewis M.; Shoolery, J. N. (1978). "Sirohydrochlorin. Prosthetic group of sulfite and nitrite reductases and its role in the biosynthesis of vitamin B12". Journal of the American Chemical Society. 100 (25): 7987–7994. doi:10.1021/ja00493a031.
  4. ^ Battersby, Alan R.; McDonald, Edward; Thompson, Mervyn; Bykhovsky, Vladimir Ya. (1978). "Biosynthesis of vitamin B12: Proof of A-B structure for sirohydrochlorin by its specific incorporation into cobyrinic acid". Journal of the Chemical Society, Chemical Communications (3): 150. doi:10.1039/C39780000150.
  5. ^ Block, Michael H.; Zimmerman, Steven C.; Henderson, Graeme B.; Turner, Simon P. D.; Westwood, Steven W.; Leeper, Finian J.; Battersby, Alan R. (1985). "Syntheses relevant to vitamin B12 biosynthesis: Synthesis of sirohydrochlorin and of its octamethyl ester". Journal of the Chemical Society, Chemical Communications (16): 1061. doi:10.1039/C39850001061.
  6. ^ Battersby, Alan R. (2000). "Tetrapyrroles: The pigments of life: A Millennium review". Natural Product Reports. 17 (6): 507–526. doi:10.1039/B002635M. PMID 11152419.