PARENT SESSION
Posters P7B Evolution of photosynthesis. Abstracts (579-591)

Artificial synthesis of Chl d from Chl a in organic solvents in the presence of Papain. Satoru WATANABE¹, Takanori GOTOH¹, Hajime KOIZUMI^*,1, Yuka ITOH¹, Hideaki MIYASHITA¹, Mamoru MIMURO², Takashi YAMASHITA², Masami KOBAYASHI¹, ¹ Inst. Materials Sci., Univ. Tsukuba, Japan² Dept. Technol. Ecol., Kyoto Univ., Japan

ABSTRACT- In 1943, Chl d was first reported by Manning and Strain as a minor pigment in several red macroalgae. In 1996, a novel cyanobacterium, Acaryochloris marina, was isolated by Miyashita et al. from colonial ascidians and was found to contain Chl d as the dominant chlorophyll. However, the biosynthesis pathway of Chl d has not been clarified yet. Chl d is thought to be synthesized from Chl a, like Chl b from Chl a, while no experimental evidence was given. We came across the formation of Chl d from Chl a in acetone or ethanol containing 10 % water in the presence of a crude Papain (EC 3.4.22.2) at room temperature in the dark. The molecular structure was confirmed by HPLC, absorption and FAB-mass analyses. Chl d was not formed when Papain was absent or other proteases (peptide hydrolase), e.g. Chymotrypsin, were used. Oxidation as well as cleavage of a C=C double bond of vinyl group (from -CH=CH₂ to -CHO) is necessary to yield Chl d from Chl a. Papain is widely known as a protease and has an active SH group. Papain has wide specificity, and sometimes functions as an esterase. In our case, Papain may function as an oxidase in organic solvents containing small amounts of water. During chemical evolution of chlorophylls, some enzyme, e.g. Papain, might play an important role. In our study, we used a crude Papain and much impurities were present. So, it is not clear whether the formation of Chl d really originated in Papain. Further studies are needed.

KEY WORDS: chlorophyll, Acaryochloris marina, Chl a, Chl d