Chlorophyll c
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][3] 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.[2]
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.[3] 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.[2]
Chlorophyll c can be further divided into chlorophyll c1, chlorophyll c2,[3] 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.[6]
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. It has been established that DV-PChlide and MV-PChlide are processed directly by a 171 oxidase (CHLC, chlorophyll c synthase) into Chl c2 and Chl c1, respectively.[8] The 171 oxidtion was proposed to proceed by "hydroxylation of the 17-propionate reside at the 171-position and successive dehydration to the 17-acrylate residue."[8][9] An 8-vinyl reductase (elaborating on the promiscuous behavior of ferredoxin-type 3,8-divinyl chlorophyllide reductase) could also convert Chl c2 into Chl c1. The two steps could be swapped for the same effect.[10]
Structure
References
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