Starter units of the biosynthesis of blepharismins: self-defense pigments of Blepharisma japonicum

The heterotrich ciliate Blepharisma japonicum produces red pigment blepharismins, which function as self-defense toxin against predators and as a photoreceptor for step-up photonegativity. The dibenzoperylenequinone moiety of blepharismins was shown to be biosynthesized via the polyketide pathway. In this paper, the starter units of the biosynthetic pathway of blepharismins were determined to be isovaleryl-CoA and butyryl-CoA by HPLC, LC/ESI-MS, and ¹H and ²H NMR analyses of the pigments obtained from feeding experiment of l-leucine or sodium butyrate in excess and deuterium-labeled l-leucine.