Fig. 1: Psilocybin biosynthesis.
The psilocybin pathway originates from l-tryptophan, which undergoes decarboxylation, oxygenation and phosphate ester formation to yield norbaeocystin, the acceptor substrate for the methyltransferase PsiM. SAM S-adenosyl-l-methionine, SAH S-adenosyl-l-homocysteine. A third methyl transfer by PsiM to yield aeruginascin has been postulated but lacks experimental evidence.
