Tetrapyrrole
Tetrapyrroles are a class of
=(CH)- or -CH
2-
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.
2-
Some tetrapyrroles form the active core of compounds with crucial
coordination compound
with the pyrroles and plays a central role in the biochemical function of those molecules.
Structure
Linear tetrapyrroles (called bilanes) include:[1]
- Heme breakdown products (e.g., bilirubin, biliverdin)
- Phycobilins (found in cyanobacteria)
- dinoflagellates and euphausiid shrimps (krill)
-
-
-
-
-
uroporphyrinogen III, an authentic tetrapyrrole
Cyclic tetrapyrroles having four one-carbon bridges include:[1]
- Porphin, the simplest tetrapyrrole
- Porphyrins, including heme, the core of hemoglobin
- Chlorins, including those at the core of chlorophyll.
Cyclic tetrapyrroles having three one-carbon bridges and one direct bond between the pyrroles include:
- cobalamins, when complexed with a cobaltion.
-
porphinmacrocycle. -
The chlorin section of the chlorophyll a molecule. The green box shows a group that varies between chlorophyll types. -
Cobalamin structure includes a corrinmacrocycle.
The tetrapyrrole portions of the molecules typically act as chromophores because of a high degree of conjugation in them. Therefore, these compounds are commonly colored.