title: Biosynthesis of the chromophore of phycobiliproteins. A study of mesohaem and mesobiliverdin as possible intermediates and further evidence for an algal haem oxygenase.
abstract: The possible roles of mesohaem and mesobiliverdin as metabolic precursors of phycocyanobilin, the chromophore of phycocyanin, were studied in the unicellular rhodophyte Cyanidium caldarium. Dark-grown cells of this organism, which had been exposed to mesohaem, were either incubated in the dark with 5-aminolaevulinate, which results in excretion of bilins into the suspending medium, or incubated in the light, which results in synthesis of phycocyanin within the cells. By using 14C-labelling, either in the mesohaem or in the 5-aminolaevulinate administered, it was shown that mesohaem is not a precursor of phycocyanobilin in either dark or light systems. However, mesohaem was converted into mesobiliverdin in both systems, a phenomenon that is further evidence for the existence of an algal haem oxygenase. The data also showed that mesobiliverdin is not a precursor of phycocyanobilin. These results suggest that algal bilins are formed via haem degradation to biliverdin in the same way as mammalian bile pigments.
mesh_terms: D000622:Aminolevulinic Acid / Q000378:metabolism; D001663:Bilirubin / Q000031:analogs & derivatives*; D001664:Biliverdine / Q000031:analogs & derivatives* / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D002855:Chromatography, Thin Layer; D003624:Darkness; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D008027:Light; D008652:Mesoporphyrins / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D052980:Phycobilins; D010798:Phycocyanin / Q000096:biosynthesis*; D010860:Pigments, Biological / Q000096:biosynthesis*; D011166:Porphyrins / Q000378:metabolism*; D011758:Pyrroles / Q000096:biosynthesis*; D000461:Rhodophyta / Q000378:metabolism*; D045725:Tetrapyrroles
chemical_list: D008652:Mesoporphyrins; D052980:Phycobilins; D010860:Pigments, Biological; D011166:Porphyrins; D011758:Pyrroles; D045725:Tetrapyrroles; D010798:Phycocyanin; C011069:phycocyanobilin; C040381:mesobiliverdin; C031468:mesoporphyrin IX; D000622:Aminolevulinic Acid; D006899:Mixed Function Oxygenases; D006419:Heme Oxygenase (Decyclizing); D001664:Biliverdine; D001663:Bilirubin