Phycobilins
Phycobilins are chromophores of photosynthesis that in cyanobacteria , glaucophyte , cryptophytes and red algae occur. Its name is derived from the similarity to the bile pigments , the bilins . The most important representatives are phycocyanobilin (in phycocyanin , blue) and phycoerythrobilin (in phycoerythrin , red). The corresponding chromoproteins , the phycobiliproteins , consist of a protein component and the chromophoric group, which, similar to the porphyrin derivatives ( chlorophyll and hemoglobin ), consist of four interconnected pyrrole rings, but not in a cyclic but in a linear arrangement. In contrast to chlorophylls and carotenoids, the chromophore is covalently bound to the protein, i.e. a prosthetic group .
For photosynthesis, the phycobilins cover wavelength ranges in which chlorophyll does not absorb. The captured energy is transferred from phycoerythrin to phycocyanin and from phycocyanin to chlorophyll. The quantum efficiency of phycobilins is even higher than that of chlorophyll.
With the help of these accessory pigments, cyanobacteria can colonize extremely low-light areas, such as the underside of river debris or the deep layers of water. You can also use the so-called green gap of chlorophyll absorption.
Occurrence
The phycobilins occur in the following proteins:
- Cyanobacteria: c -phycoerythrin, c-phycocyanin, allophycocyanin and phycoerythrocyanin
- Glaucophyta: c -phycocyanin and allophycocyanin
- Cryptophyta: Phycoerythrin-545 and r -Phycocyanin
- Red algae: r -phycocyanin, r, b -phycoerythrin, allophycocyanin
literature
- Heath, OVS: Physiology of Photosynthesis . Thieme 1972, ISBN 3-13-490101-3
- Laura Barsanti and Paolo Gualteri: Algae: Anatomy, Biochemistry, and Biotechnology , Boca Raton, Fla. [u. a.]: Taylor & Francis, 2006, ISBN 0-8493-1467-4