Psilocybin, the main psychoactive compound in magic mushrooms, is also produced by some Inocybe species. Researchers characterized four enzymes from Inocybe corydalina and found that none of the reactions used in Psilocybe species occur in this species. Instead, the Inocybe pathway is branched and produces baeocystin as a second end product. These results show that mushrooms evolved the ability to make psilocybin twice independently, using distantly related or entirely different enzymes.
Psilocybin, the main psychoactive alkaloid in magic mushrooms, is produced by several fungal genera. In Psilocybe species the biosynthetic pathway from L-tryptophan is well characterized. This work examined the pathway in Inocybe corydalina, a distantly related mushroom that also makes psilocybin. Four recombinant enzymes from I. corydalina were characterized in vitro: a decarboxylase (IpsD), a kinase (IpsK), and two methyltransferases (IpsM1 and IpsM2); a fifth monooxygenase (IpsH) was analyzed in silico. None of the reactions matched those in Psilocybe. The Inocybe pathway is branched and also produces baeocystin as a second end product. The findings indicate that psilocybin biosynthesis evolved twice independently using unrelated enzymes.