Phycobilin

Phycobilins are chromophores in photosynthesis that occur in cyanobacteria, Glaucophyta, cryptophytes and red algae. Your name is derived from the similarity to the bile pigments, the bilinen. The most important representatives are phycocyanobilin ( in phycocyanin, blue) and phycoerythrobilin ( in phycoerythrin, red). The corresponding chromoproteins, the phycobiliproteins are composed of a protein moiety and the chromophore group, which is similar to the porphyrin ( chlorophyll and hemoglobin) consist of four pyrrole rings connected together, but not in cyclic, but in a linear arrangement. The chromophore is in contrast to chlorophylls and carotenoids covalently bound to the protein, which is a prosthetic group.

The phycobilins cover for photosynthesis wavelength ranges in which the chlorophyll is not absorbed. The captured energy is transferred from phycoerythrin to phycocyanin and, where appropriate, of phycocyanin to chlorophyll. The quantum efficiency of phycobilins is even higher than that of chlorophyll.

With the help of these accessory pigments blue-green algae can colonize pronounced low-light areas, such as the underside of river gravel or the deep layers of waters. You can use the so-called green gap of the chlorophyll absorption thereby further.

Occurrence

The phycobilins come in the following proteins before:

• Cyanobacteria: c- phycoerythrin, C- phycocyanin, allophycocyanin and phycoerythrocyanine
• Glaucophyta: c- phycocyanin and allophycocyanin
• Cryptophytes: phycoerythrin -545 and r- phycocyanin
• Red algae: R- phycocyanin, R, B -phycoerythrin, allophycocyanin