Calyculin biogenesis from a pyrophosphate protoxin produced by a sponge symbiont.

The Japanese marine sponge Discodermia calyx contains a major cytotoxic compound, calyculin A, which exhibits selective inhibition of protein phosphatases 1 and 2A. It has long been used as a chemical tool to evaluate intracellular signal transduction regulated by reversible protein phosphorylation. We describe the identification of the biosynthetic gene cluster of calyculin A by a metagenome mining approach.