Biosynthesis of phycobilins. 15,16-Dihydrobiliverdin IX alpha is a partially reduced intermediate in the formation of phycobilins from biliverdin IX alpha.
A partially purified protein fraction from the phycocyanin-containing unicellular rhodophyte, Cyanidium caldarium, reductively transforms biliverdin IX alpha to a violet colored bilin in the presence of NADPH, ferredoxin, and ferredoxin-NADP+ reductase. This bilin has a violin-like absorption spectrum with maxima at 335 and 560 nm in methanolic HCl and at 337, 567, and 603-604 nm in CHCl3. The bilin has been determined to be 15,16-dihydrobiliverdin IX alpha by comparative spectrophotometry and 1H NMR spectroscopy. This product of biliverdin IX alpha reduction is converted enzymatically to phycobilins by further reduction. A general biosynthetic pathway is proposed which accounts for the formation of the phycobilins from biliverdin IX alpha by a two-step reduction process followed by isomerization.
Beale
S I
SI
Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912.
Cornejo
J
J
D001664:Biliverdine / Q000031:analogs & derivatives* / Q000378:metabolism*; D002850:Chromatography, Gel; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010084:Oxidation-Reduction; D052980:Phycobilins; D010798:Phycocyanin / Q000096:biosynthesis*; D011758:Pyrroles / Q000378:metabolism*; D000461:Rhodophyta / Q000201:enzymology*; D013053:Spectrophotometry; D045725:Tetrapyrroles
D052980:Phycobilins; D011758:Pyrroles; D045725:Tetrapyrroles; D010798:Phycocyanin; C071708:15,16-dihydrobiliverdin IXa; C011069:phycocyanobilin; D001664:Biliverdine