Psilocybin, a psychedelic alkaloid, can account for up to 2% of the dry mass of Psilocybe mushrooms, creating a high demand for its precursor L-tryptophan during carpophore (fruiting body) formation. Using Psilocybe mexicana, researchers found that genes for L-tryptophan biosynthesis (trpE1, trpD, trpB) were upregulated in carpophores, while genes for L-tryptophan-consuming pathways (idoA, iasA) were massively downregulated. The IasA enzyme was characterized as the first microbial L-tryptophan-preferring acetaldehyde synthase. Comparison with Psilocybe cubensis revealed species-specific differences in regulation. This coordination of primary and secondary metabolism routes L-tryptophan toward psilocybin production, providing initial insight into how Basidiomycota manage metabolic flux.
Psilocybe 'magic mushrooms' are well known for their psychotropic tryptamines, but the diversity of other specialized metabolites, especially terpenoids, has remained unclear. CubA, the single clade II sesquiterpene synthase from Psilocybe cubensis, was produced in Escherichia coli and characterized in vitro, with additional in vivo assays in Aspergillus niger. GC-MS analyses showed CubA functions as a multi-product synthase, producing cubebol, β-copaene, δ-cadinene, and germacrene D as major products depending on reaction conditions. Analysis of mature P. cubensis mushrooms detected β-copaene and δ-cadinene. Closely related enzymes are encoded in genomes of various Psilocybe species, providing insight into the metabolic capacity of the entire genus.