Chlorophyll c explained

Chlorophyll c refers to forms of chlorophyll found in certain marine algae, including the photosynthetic Chromista (e.g. diatoms and brown algae) and dinoflagellates.[1] [2] These pigments are characterized by their unusual chemical structure, with a porphyrin as opposed to the chlorin (which has a reduced ring D) as the core; they also do not have an isoprenoid tail. Both these features stand out from the other chlorophylls commonly found in algae and plants.[3]

It has a blue-green color and is an accessory pigment, particularly significant in its absorption of light in the 447 - 520 nm wavelength region. Like chlorophyll a and chlorophyll b, it helps the organism gather light and passes a quanta of excitation energy through the light harvesting antennae to the photosynthetic reaction centre.[3]

Chlorophyll c can be further divided into chlorophyll c1, chlorophyll c2,[2] and chlorophyll c3,[4] plus at least eight other more recently found subtypes.[5]

Chlorophyll c1

Chlorophyll c1 is a common form of chlorophyll c. It differs from chlorophyll c2 in its C8 group, having an ethyl group instead of vinyl group (C-C single bond instead of C=C double bond).Its absorption maxima are around 444, 577, 626 nm and 447, 579, 629 nm in diethyl ether and acetone respectively.[6]

Chlorophyll c2

Chlorophyll c2 is the most common form of chlorophyll c.[7] Its absorption maxima are around 447, 580, 627 nm and 450, 581, 629 nm in diethyl ether and acetone respectively.

Chlorophyll c3

Chlorophyll c3 is a form of chlorophyll c found in microalga Emiliania huxleyi, identified in 1989.[4] Its absorption maxima are around 452, 585, 625 nm and 452, 585, 627 nm in diethyl ether and acetone respectively.[6]

Biosynthesis

Chlorophyll c synthesis branches off early from the typical Chlorophyllide synthesis pathway, after divinylprotochlorophyllide (DV-PChlide) is formed. DV-PChlide can be processed directly by an unidentified 171 oxidase into Chl c2. An 8-vinyl reductase (elaborating on the promiscuous behavior of ferredoxin-type 3,8-divinyl chlorophyllide reductase) could then convert Chl c2 into Chl c1. The two steps could be swapped for the same effect.[8]

The 171 oxidtion appears to proceed by "hydroxylation of the 17-propionate reside at the 171-position and successive dehydration to the 17-acrylate residue."[9]

Notes and References

  1. Web site: Speer . B. R. . Photosynthetic Pigments . 2 August 2014.
  2. Dougherty RC, Strain HH, Svec WA, Uphaus RA, Katz JJ . The structure, properties, and distribution of chlorophyll c . . 92 . 9 . 2826–33 . May 1970 . 5439971 . 10.1021/ja00712a037.
  3. Book: Blankenship, Robert E. . Robert E. Blankenship . vanc . Molecular Mechanisms of Photosynthesis . February 2002 . Wiley-Blackwell.
  4. Fookes CJ, Jeffrey SW . The structure of chlorophyll c3, a novel marine photosynthetic pigment . J. Chem. Soc., Chem. Commun. . 1989 . 23 . 1827–28 . 10.1039/C39890001827.
  5. Zapata . Manuel . Garrido . José L. . Jeffrey . Shirley W. . vanc . Chlorophyll c Pigments: Current Status . Chlorophylls and Bacteriochlorophylls: Advances in Photosynthesis and Respiration . 2006 . 25 . 39–53 . 10.1007/1-4020-4516-6_3 . Advances in Photosynthesis and Respiration . 978-1-4020-4515-8.
  6. Fawley MW . A new form of chlorophyll C involved in light-harvesting . Plant Physiology . 91 . 2 . 727–32 . October 1989 . 16667093 . 1062062 . 10.1104/pp.91.2.727 .
  7. Jeffrey SW . The Occurrence of Chlorophyll c1 and c2 in Algae. Journal of Phycology. September 1976. 12. 3. 349–354. 10.1111/j.1529-8817.1976.tb02855.x. 83927313 .
  8. Ito . Hisashi . Tanaka . Ayumi . Evolution of a New Chlorophyll Metabolic Pathway Driven by the Dynamic Changes in Enzyme Promiscuous Activity . Plant and Cell Physiology . March 2014 . 55 . 3 . 593–603 . 10.1093/pcp/pct203 . 24399236. 2115/58225 . free .
  9. Xu . M . Kinoshita . Y . Matsubara . S . Tamiaki . H . Synthesis of chlorophyll-c derivatives by modifying natural chlorophyll-a. . Photosynthesis Research . March 2016 . 127 . 3 . 335–45 . 10.1007/s11120-015-0190-1 . 26346903. 254944200 .