Tetrapyrroles are a class of chemical compounds whose molecules consist of four pyrrole rings linked together directly or through single-carbon bridges (= (CH) - or -CH 2 -), forming a cyclic or linear structure. In cyclic tetrapyrroles, the lone electron pair on the nitrogen atom, directed to the center of the macrocyclic ring, can form covalent or coordination bonds with ions of metals such as iron , cobalt , or magnesium .
The tetrapyrrols that have important biological significance include such molecules as heme and chlorophyll ). In particular, in these two molecules, the macrocyclic ring forms a coordination compound with metal ions, which play an important role in the functioning of these molecules.
Structure
By linear tetrapyrrole (referred to as bilanami ) include: [1]
- Heme degradation products ( bilirubin , biliverdin )
- Ficobilins (found in cyanobacteria )
| Bilirubin | Biliverdin | Phycoerythrobilin |
By cyclic tetrapyrrole, connected by four one-carbon bridges include: [1]
- Porphyrins , including heme
- Chlorins , including most of the chlorophylls
Cyclic tetrapyrrols with three one-carbon bridges and one direct connection between pyrroles include:
- Corrins including cobalamin core
| Heme | Chlorophyll | Cyancobalamin |
Due to the high amount of conjugated bonds, tetrapyrrole exhibit the properties of chromophores and are usually well colored.
Notes
- 2 1 2 Nomenclature of Tetrapyrroles, Appendix 1. Trivially named porphyrins, chlorins, chlorophylls and bilins, fundamental parents (Not available link) . The appeal date is January 24, 2015. Archived October 25, 2012.