Chlorophyll b

Chlorophyll b

Structure of β-Chlorophyll
Names
IUPAC name Chlorophyll b
Systematic IUPAC name Magnesium [methyl (3S,4S,21R)-14-ethyl-13-formyl-4,8,18-trimethyl-20-oxo-3-(3-oxo-3-{[(2E,7R,11R)-3,7,11,15-tetramethyl-2-hexadecen-1-yl]oxy}propyl)-9-vinyl-21-phorbinecarboxylatato(2-)-κ2N,N′]
Other names β-Chlorophyll
Identifiers
CAS Number	519-62-0  N
3D model (JSmol)	Interactive image
ChemSpider	16739843  Y
ECHA InfoCard	100.007.522
EC Number	208-272-4
E number	E140 (colours)
PubChem CID	6450186 11593175  (from spinach)
UNII	5712ZB110R  N
CompTox Dashboard (EPA)	DTXSID70889349
InChI InChI=1S/C55H71N4O6.Mg/c1-12-38-35(8)42-27-43-36(9)40(23-24-48(61)65-26-25-34(7)22-16-21-33(6)20-15-19-32(5)18-14-17-31(3)4)52(58-43)50-51(55(63)64-11)54(62)49-37(10)44(59-53(49)50)28-46-39(13-2)41(30-60)47(57-46)29-45(38)56-42;/h12,25,27-33,36,40,51H,1,13-24,26H2,2-11H3,(H-,56,57,58,59,60,62);/q-1;+2/p-1/b34-25+;/t32-,33-,36+,40+,51-;/m1./s1 Y Key: NSMUHPMZFPKNMZ-VBYMZDBQSA-M Y InChI=1S/C55H72N4O6.Mg/c1-12-38-35(8)42-27-43-36(9)40(23-24-48(61)65-26-25-34(7)22-16-21-33(6)20-15-19-32(5)18-14-17-31(3)4)52(58-43)50-51(55(63)64-11)54(62)49-37(10)44(59-53(49)50)28-46-39(13-2)41(30-60)47(57-46)29-45(38)56-42;/h12,25,27-33,36,40,51H,1,13-24,26H2,2-11H3,(H2,56,57,58,59,60,62);/q;+2/p-2/b34-25+;/t32-,33-,36+,40+,51-;/m1./s1 Key: MSLKMRUEVOYOOZ-VBYMZDBQSA-L
SMILES CCC1=C(C2=NC1=CC3=C(C4=C([N-]3)C(=C5[C@H]([C@@H](C(=N5)C=C6C(=C(C(=C2)[N-]6)C=C)C)C)CCC(=O)OC/C=C(\C)/CCC[C@H](C)CCC[C@H](C)CCCC(C)C)[C@H](C4=O)C(=O)OC)C)C=O.[Mg+2]
Properties
Chemical formula	C55H70MgN4O6
Molar mass	907.492 g·mol−1
Appearance	Green
Odor	Odorless
Melting point	~125 °C (257 °F; 398 K) [1]
Solubility in water	Insoluble [1]
Solubility	Very soluble in ethanol, ether, pyridine Soluble in methanol [1]
Absorbance	See text
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N  verify  (what is  YN ?) Infobox references

The absorption spectrum of both the chlorophyll a and the chlorophyll b pigments. The use of both together enhances the size of the absorption of light for producing energy.

Chlorophyll b is a form of chlorophyll. Chlorophyll b helps in photosynthesis by absorbing light energy. It is more soluble than chlorophyll a in polar solvents because of its carbonyl group. Its color is green, and it primarily absorbs blue light. ^[2]

In land plants, the light-harvesting antennae around photosystem II contain the majority of chlorophyll b. Hence, in shade-adapted chloroplasts, which have an increased ratio of photosystem II to photosystem I, there is a higher ratio of chlorophyll b to chlorophyll a. ^[3] This is adaptive, as increasing chlorophyll b increases the range of wavelengths absorbed by the shade chloroplasts.

Structure of chlorophyll b molecule showing the long hydrocarbon tail

Biosynthesis

Main article: Chlorophyllide

The Chlorophyll b biosynthetic pathway utilizes a variety of enzymes. ^[4] In most plants, chlorophyll is derived from glutamate and is synthesised along a branched pathway that is shared with heme and siroheme. ^{[5] [6] [7]} The initial steps incorporate glutamic acid into 5-aminolevulinic acid (ALA); two molecules of ALA are then reduced to porphobilinogen (PBG), and four molecules of PBG are coupled, forming protoporphyrin IX.

Chlorophyll synthase ^[8] is the enzyme that completes the biosynthesis of chlorophyll b ^{[9] [10]} by catalysing the reaction EC 2.5.1.62

chlorophyllide b + phytyl diphosphate ${\displaystyle \rightleftharpoons }$ chlorophyll b + diphosphate

This forms an ester of the carboxylic acid group in chlorophyllide b with the 20-carbon diterpene alcohol phytol.

References

1. Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN   978-1-4200-9084-0.
2. "Photosynthesis pigments". Archived from the original on 2012-09-05. Retrieved 2011-01-13.
3. Kitajima, Kaoru; Hogan, Kevin P (2003). "Increases of chlorophyll a/b ratios during acclimation of tropical woody seedlings to nitrogen limitation and high light". Plant, Cell & Environment. 26 (6): 857–865. doi: 10.1046/j.1365-3040.2003.01017.x . PMID   12803613.
4. Suzuki JY, Bollivar DW, Bauer CE (1997). "Genetic analysis of chlorophyll biosynthesis". Annual Review of Genetics. 31 (1): 61–89. doi:10.1146/annurev.genet.31.1.61. PMID   9442890.
5. Battersby, A. R. (2000). "Tetrapyrroles: the Pigments of Life. A Millennium review". Nat. Prod. Rep. 17 (6): 507–526. doi:10.1039/B002635M. PMID   11152419.
6. Akhtar, M. (2007). "The Modification of Acetate and Propionate Side Chains During the Biosynthesis of Haem and Chlorophylls: Mechanistic and Stereochemical Studies". Ciba Foundation Symposium 180 - the Biosynthesis of the Tetrapyrrole Pigments. Novartis Foundation Symposia. Vol. 180. pp. 131–155. doi:10.1002/9780470514535.ch8. ISBN   9780470514535. PMID   7842850.
7. Willows, Robert D. (2003). "Biosynthesis of chlorophylls from protoporphyrin IX". Natural Product Reports. 20 (6): 327–341. doi:10.1039/B110549N. PMID   12828371.
8. Schmid, H. C.; Rassadina, V.; Oster, U.; Schoch, S.; Rüdiger, W. (2002). "Pre-Loading of Chlorophyll Synthase with Tetraprenyl Diphosphate is an Obligatory Step in Chlorophyll Biosynthesis" (PDF). Biological Chemistry. 383 (11): 1769–78. doi:10.1515/BC.2002.198. PMID   12530542. S2CID   3099209.
9. Eckhardt, Ulrich; Grimm, Bernhard; Hortensteiner, Stefan (2004). "Recent advances in chlorophyll biosynthesis and breakdown in higher plants" . Plant Molecular Biology. 56 (1): 1–14. doi:10.1007/s11103-004-2331-3. PMID   15604725. S2CID   21174896.
10. Bollivar, David W. (2007). "Recent advances in chlorophyll biosynthesis". Photosynthesis Research. 90 (2): 173–194. doi:10.1007/s11120-006-9076-6. PMID   17370354. S2CID   23808539.