Conversion of Chl a into Chl d by Heat-Treated Papain
In 1943, Chl d was first reported as a minor pigment in several red macroalgae. In 1996, a novel cyanobacterium, Acaryochloris marina, was isolated from colonial ascidians, and A. marina 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, while no experimental evidence was given. In 2004, we came across the formation of Chl d from Chl a in acetone or ethanol containing 10 % water in the presence of papain (EC 184.108.40.206) at room temperature in the dark. Chl d was not formed when papain was absent. Here we report the conversion of Chl a into Chl d in aqueous acetone at room temperature in the presence of papain treated at 96°C for 20 min. The yield of Chl d from Chl a did not change, when the heat-treated papain was used. The result indicate that conversion of Chl a into Chl d was not enzymatically caused by papain, but by something else contained in commercially available papain.
KeywordsAcaryochloris marina chlorophyll a chlorophyll d photodynamic therapy (PDT) photosensitizer photosynthesis
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