Phycocyanobilin

Phycocyanobilin

Names
IUPAC name (2R,3E)-18-ethyl-3-ethylidene-1,2,3,19,22,24-hexahydro-2,7,13,17-tetramethyl-1,19-dioxo-21H-biline-8,12-dipropanoic acid
Identifiers
CAS Number	20298-86-6  Y
3D model (JSmol)	Interactive image
Beilstein Reference	4285356
ChEBI	CHEBI:48863
ChemSpider	16736730
PubChem CID	5460417
UNII	36NUT04V2K  Y
CompTox Dashboard (EPA)	DTXSID401107685
InChI InChI=1S/C33H38N4O6/c1-7-20-19(6)32(42)37-27(20)14-25-18(5)23(10-12-31(40)41)29(35-25)15-28-22(9-11-30(38)39)17(4)24(34-28)13-26-16(3)21(8-2)33(43)36-26/h7,13-15,19,35H,8-12H2,1-6H3,(H,36,43)(H,37,42)(H,38,39)(H,40,41)/b20-7+,26-13-,27-14-,28-15-/t19-/m1/s1 Y Key: INPDFIMLLXXDOQ-UAWLBFNISA-N Y
SMILES C/C=C1C(=C/c2[nH]c(/C=C3\N=C(/C=C4\NC(=O)C(CC)=C4C)C(C)=C3CCC(=O)O)c(CCC(=O)O)c2C)/NC(=O)[C@@H]/1C
Properties
Chemical formula	C33H38N4O6
Molar mass	586.69 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Phycocyanobilin is a blue phycobilin, i.e., a tetrapyrrole chromophore found in cyanobacteria and in the chloroplasts of red algae, glaucophytes, and some cryptomonads. Phycocyanobilin is present only in the phycobiliproteins allophycocyanin and phycocyanin, of which it is the terminal acceptor of energy. It is covalently linked to these phycobiliproteins by a thioether bond.

Phycocyanobilin (PCB), has the ability to bind to human serum albumin (HSA), protein found mainly in the blood of humans. This PCB-HCA complex benefits the structure of HSA, increasing the thermal stability of HSA, as well as increasing its ability to prevent against proteolytic activity of other proteins. ^[1]

Biosynthetic Pathway

Scheme illustrating the different steps of the biosynthesis of phycocyanobilin

The biosynthetic pathway of phycocyanobilin begins with 5-aminolevulinic acid (5-ALA). ^[2] Two molecules of 5-ALA undergo a condensation reaction catalyzed by porphobilinogen synthase to yield a molecule of porphobilinogen (PBG) (not shown). ^[3] Four molecules of PBG are polymerized into a linear tetrapyrrole by porphobilinogen deaminase. This reaction releases four ammonia molecules in the process. Completion of the tetrapyrrole is performed by uroporphyrinogen III synthase which results in the macrocyclic Uroporphyrinogen III. Uroporphyrinogen III is then converted to a heme by uroporphyrinogen III decarboxylase. The heme molecule is converted to biliverdin. This is reduced to phycocyanobilin by phycocyanobilin:ferredoxin oxidoreductase PcyA. ^{[4] [2]}

Biological role

Phycocyanobilin is a component of phycobilisome protein complexes, the light-harvesting antennae that transmit the energy of photons to photosystem II and photosystem I in cyanobacteria and in the chloroplasts of red algae and glaucophytes. ^{[5] [6]} The absorption spectrum of phycocyanobilin in the 500–650 nm range where chlorophyll absorbs poorly allows organisms such as Galdieria sulphuraria which use it to be more efficient. ^[7]

The tetrapyrrole is covalently attached to the phycobiliprotein through a bond between the sulfur of a cysteine amino-acid and the ring-C=CCH₃ sidechain, as a thioether. ^{[4] [8]}

Uses

Phycocyanobilin and the related phycoerythrobilins, in the form of phycobiliproteins, are widely used in foodstuffs and cosmetics as colourants. They are mainly obtained from Spirulina species. ^[9]

References

1. Radibratovic M, Minic S, Stanic-Vucinic D, Nikolic M, Milcic M, Cirkovic Velickovic T (2016-12-13). "Stabilization of Human Serum Albumin by the Binding of Phycocyanobilin, a Bioactive Chromophore of Blue-Green Alga Spirulina: Molecular Dynamics and Experimental Study". PLOS ONE. 11 (12) e0167973. Bibcode:2016PLoSO..1167973R. doi: 10.1371/journal.pone.0167973 . PMC   5154526 . PMID   27959940.
2. Brown, Stanley B.; Houghton, Jennifer D.; Vernon, David I. (1990-04-01). "New trends in photobiology biosynthesis of phycobilins. Formation of the chromophore of phytochrome, phycocyanin and phycoerythrin". Journal of Photochemistry and Photobiology B: Biology. 5 (1): 3–23. doi:10.1016/1011-1344(90)85002-E. ISSN   1011-1344. PMID   2111391.
3. Watanabe, Fumio; Yabuta, Yukinori; Bito, Tomohiro (2014-01-01), Atta-ur-Rahman (ed.), Chapter 11 - Tetrapyrrole Compounds of Cyanobacteria , Studies in Natural Products Chemistry, vol. 42, Elsevier, pp. 341–351, doi:10.1016/b978-0-444-63281-4.00011-2, ISBN   978-0-444-63281-4, archived from the original on 2024-03-20, retrieved 2023-06-08
4. Beale, Samuel I. (1993). "Biosynthesis of phycobilins". Chemical Reviews. 93 (2): 785–802. doi:10.1021/cr00018a008.
5. Kawakami K, Hamaguchi T, Hirose Y, Kosumi D, Miyata M, Kamiya N, Yonekura K (2022). "Core and rod structures of a thermophilic cyanobacterial light-harvesting phycobilisome". Nature Communications. 13 (1) 3389: 3389. Bibcode:2022NatCo..13.3389K. doi: 10.1038/s41467-022-30962-9 . PMC   9205905 . PMID   35715389.
6. Chang L, Liu X, Li Y, Liu CC, Yang F, Zhao J, Sui SF (2015). "Structural organization of an intact phycobilisome and its association with photosystem II". Cell Research. 25 (6): 726–737. doi:10.1038/cr.2015.59. PMC   4456626 . PMID   25998682.
7. Frascogna, Federica; Rockwell, Nathan C.; Hartmann, Jana; Mudler, Julie M.; Frankenberg-Dinkel, Nicole (2026). "Phycocyanobilin biosynthesis in Galdieria sulphuraria requires isomerization of phycoerythrobilin synthesized by bilin reductases". The FEBS Journal febs.70391. doi: 10.1111/febs.70391 .
8. Sepúlveda-Ugarte, José; Brunet, Juan E.; Matamala, Adelio R.; Martínez-Oyanedel, José; Bunster, Marta (2011). "Spectroscopic parameters of phycoerythrobilin and phycourobilin on phycoerythrin from Gracilaria chilensis" (PDF). Journal of Photochemistry and Photobiology A: Chemistry. 219 (2–3): 211–216. doi:10.1016/j.jphotochem.2011.02.012.
9. Ji, Liang; Qiu, Sheng; Wang, Zhiheng; Zhao, Chenni; Tang, Bo; Gao, Zhengquan; Fan, Jianhua (2023). "Phycobiliproteins from algae: Current updates in sustainable production and applications in food and health". Food Research International. 167 112737. doi:10.1016/j.foodres.2023.112737. PMID   37087221.