Tetrapyrroles are a class of
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s 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 carbon atoms and one nitrogen atom. Tetrapyrroles are common cofactors in biochemistry and their biosynthesis and degradation feature prominently in the chemistry of life.
Some tetrapyrroles form the active core of compounds with crucial
biochemical roles in living systems, such as
hemoglobin
Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...
and
chlorophyll. In these two molecules, in particular, the pyrrole
macrocycle
Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry.
...
ring frames a metal atom, that forms a
coordination compound with the pyrroles and plays a central role in the biochemical function of those molecules.
Structure
Linear tetrapyrroles (called
bilane
In organic chemistry, bilane is a compound with the formula or . It is a tetrapyrrole, a class of compounds with four independent pyrrole rings. Specifically, the molecule can be described as four pyrrole molecules connected in an open chain by ...
s) include:
[Nomenclature of Tetrapyrroles, Appendix 1. Trivially named porphyrins, chlorins, chlorophylls and bilins, fundamental parents](_blank)
/ref>
*Heme breakdown products (e.g., bilirubin, biliverdin
Biliverdin (latin for green bile) is a green tetrapyrrolic bile pigment, and is a product of heme catabolism.Boron W, Boulpaep E. Medical Physiology: a cellular and molecular approach, 2005. 984-986. Elsevier Saunders, United States. It is the ...
)
* Phycobilins (found in cyanobacteria)
*Luciferin
Luciferin (from the Latin ''lucifer'', "light-bearer") is a generic term for the light-emitting compound found in organisms that generate bioluminescence. Luciferins typically undergo an enzyme-catalyzed reaction with molecular oxygen. The resul ...
s as found in dinoflagellates
The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates a ...
and euphausiid shrimps (krill)
File:Bilirubin ZZ.png, Bilirubin
File:Biliverdin3.svg, Biliverdin
Biliverdin (latin for green bile) is a green tetrapyrrolic bile pigment, and is a product of heme catabolism.Boron W, Boulpaep E. Medical Physiology: a cellular and molecular approach, 2005. 984-986. Elsevier Saunders, United States. It is the ...
File:Phycoerythrobilin.svg, Phycoerythrobilin
File:Luciferin dinoflagellate.svg, Dinoflagellate (R=H) and krill
Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish.
Krill are consi ...
(R=OH) luciferin
Luciferin (from the Latin ''lucifer'', "light-bearer") is a generic term for the light-emitting compound found in organisms that generate bioluminescence. Luciferins typically undergo an enzyme-catalyzed reaction with molecular oxygen. The resul ...
File:Uroporphyrinogen III skeletal.svg, 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 uroporphy ...
, an authentic tetrapyrrole
Cyclic tetrapyrroles having four one-carbon bridges include:Porphin
Porphine or porphin is an organic chemical compound with formula . The molecule, which is flat, consists of four pyrrole-like rings joined by four methine (= C H−) groups to form a larger macrocycle ring, which makes it the simplest of the tet ...
, the simplest tetrapyrrole
*Porphyrin
Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical com ...
s, including heme
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 "consis ...
, the core of hemoglobin
*Chlorin
In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins. The parent chlorin is an unstable compound which undergoes air oxidation to porphine.
The name chlorin derives from chlorophyll. Chlorophyll ...
s, including those at the core of chlorophyll.
Cyclic tetrapyrroles having three one-carbon bridges and one direct bond between the pyrroles include:
*Corrin
Corrin is a heterocyclic compound. It is the parent macrocycle related to the substituted derivative that is found in vitamin B12. Its name reflects that it is the "core" of vitamin B12 (cobalamins).Nelson, D. L.; Cox, M. M. "Lehninger, Princi ...
s, including the cores of cobalamin
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
s, when complexed with a cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...
ion.
File:Heme.svg, Heme
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 "consis ...
group of hemoglobin with a porphin
Porphine or porphin is an organic chemical compound with formula . The molecule, which is flat, consists of four pyrrole-like rings joined by four methine (= C H−) groups to form a larger macrocycle ring, which makes it the simplest of the tet ...
macrocycle.
File:C-3 position Chlorophyll a.svg, The chlorin
In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins. The parent chlorin is an unstable compound which undergoes air oxidation to porphine.
The name chlorin derives from chlorophyll. Chlorophyll ...
section of the chlorophyll a molecule. The green box shows a group
A group is a number of persons or things that are located, gathered, or classed together.
Groups of people
* Cultural group, a group whose members share the same cultural identity
* Ethnic group, a group whose members share the same ethnic ide ...
that varies between chlorophyll types.
File:Cobalamin.svg, Cobalamin
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
structure includes a corrin
Corrin is a heterocyclic compound. It is the parent macrocycle related to the substituted derivative that is found in vitamin B12. Its name reflects that it is the "core" of vitamin B12 (cobalamins).Nelson, D. L.; Cox, M. M. "Lehninger, Princi ...
macrocycle.
The tetrapyrrole portions of the molecules typically act as chromophores because of a high degree of conjugation
Conjugation or conjugate may refer to:
Linguistics
* Grammatical conjugation, the modification of a verb from its basic form
* Emotive conjugation or Russell's conjugation, the use of loaded language
Mathematics
* Complex conjugation, the chang ...
in them. Therefore, these compounds are commonly colored.
References
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