Abstract
Chlorophyll(Chl)-c is widely distributed in oxygenic photosynthetic organisms and is supposed to be a light-harvesting pigment in photosynthesis. Comparing to other chlorophyllous pigments, the pigment is quite unique in its structure. Chl-c is characterized by a fully conjugated porphyrin skeleton as well as an acrylic residue at the 17-position. However, the details of distribution of the stereoisomers at the chiral 132-position (prime (132S) and non-prime (132R) types of Chls) and photosynthetic functions have not yet been clarified. We established the method for determination of the stereochemistry by chiral HPLC and CD spectra. To generalize natural selection of (132R)- and/or (132S)-enantiomers of Chl-c, we analyzed various classes of photosynthetic organisms containing Chl-c based on the method. The (132R)-enantiomer could be exclusively observed for all organisms investigated here. The results strongly indicate that Chl-c functions as a light-absorbing pigment in photosynthesis together with the other pigments, Chl-a and carotenoids. This natural selection was consistent with that of Chl-b found as an accessory pigment in plant.
