Sirohydrochlorin is a
tetrapyrrole
Tetrapyrroles are a class of chemical compounds that contain four pyrrole or pyrrole-like rings. The pyrrole/pyrrole derivatives are linked by ( =- or -- units), in either a linear or a cyclic fashion. Pyrroles are a five-atom ring with four ca ...
macrocyclic metabolic intermediate
Metabolic intermediates are molecules that are the precursors or metabolites of biologically significant molecules.
Although these intermediates are of relatively minor direct importance to cellular function, they can play important roles in the a ...
in the
biosynthesis of
sirohaem, the iron-containing prosthetic group in
sulfite reductase enzymes. It is also the
biosynthetic precursor to
cofactor F430
F430 is the cofactor (sometimes called the coenzyme) of the enzyme methyl coenzyme M reductase (MCR).
MCR catalyzes the reaction that releases methane in the final step of methanogenesis:
: + HS–CoB → + CoB–S–S–CoM
It is found ...
, an enzyme which catalyzes the release of methane in the final step of
methanogenesis
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a gro ...
.
Structure
Sirohydrochlorin was first isolated in the early 1970s when it was shown to be the metal-free form of the
prosthetic group
A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein.
Not to be confused with the cofactor that binds to the enzyme apoenzyme (eithe ...
in the
ferredoxin-nitrite reductase from spinach. Its chemical identity was established by spectroscopy and by total synthesis.
Biosynthesis
Sirohydrochlorin is derived from a tetrapyrrolic structural framework created by the enzymes
deaminase and
cosynthetase which transform
aminolevulinic acid
δ-Aminolevulinic acid (also dALA, δ-ALA, 5ALA or 5-aminolevulinic acid), an endogenous non-proteinogenic amino acid, is the first compound in the porphyrin synthesis pathway, the pathway that leads to heme in mammals, as well as chlorophyll in ...
via
porphobilinogen
Porphobilinogen (PBG) is an organic compound that occurs in living organisms as an intermediate in the biosynthesis of porphyrins, which include critical substances like hemoglobin and chlorophyll.
The structure of the molecule can be described a ...
and
hydroxymethylbilane
Hydroxymethylbilane, also known as preuroporphyrinogen, is an organic compound that occurs in living organisms during the synthesis of porphyrins, a group of critical substances that include haemoglobin, myoglobin, and chlorophyll. The name is ofte ...
to
uroporphyrinogen III
Uroporphyrinogen III is a tetrapyrrole, the first macrocyclic intermediate in the biosynthesis of heme, chlorophyll, vitamin B12, and siroheme. It is a colorless compound, like other porphyrinogens.
Structure
The molecular structure of uropo ...
. The latter is the first macrocyclic intermediate common to
haem
Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver.
In biochemical terms, heme is a coordination complex "consist ...
,
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to ...
, 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.
See also
*
Sirohydrochlorin ferrochelatase an enzyme that catalyzes insertion of iron to form siroheme.
*
Sirohydrochlorin cobaltochelatase an enzyme that catalyzes insertion of cobalt.
References
{{Tetrapyrroles
Tetrapyrroles