Iterative l‐Tryptophan Methylation in Psilocybe Evolved by Subdomain Duplication
Felix Blei, Janis Fricke, Jonas Wick, Jason C. Slot, Dirk Hoffmeister
ChemBioChem August 11, 2018 DOI: 10.1002/cbic.201800336 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Experimental study Peer reviewed |
|---|---|
| Topics | Psilocybin |
| Keywords | Tryptamine Biochemistry Biosynthesis Tryptophan Enzyme Gene |
| Citations | 31 |
| Key findings | A second methyltransferase, TrpM, mono- and dimethylates L-tryptophan in Psilocybe serbica, revealing an alternative L-tryptophan-dependent pathway not involved in psilocybin biosynthesis. |
Abstract
Abstract Psilocybe mushrooms are best known for their l ‐tryptophan‐derived psychotropic alkaloid psilocybin. Dimethylation of norbaeocystin, the precursor of psilocybin, by the enzyme PsiM is a critical step during the biosynthesis of psilocybin. However, the “magic” mushroom Psilocybe serbica also mono‐ and dimethylates l ‐tryptophan, which is incompatible with the specificity of PsiM. Here, a second methyltransferase, TrpM, was identified and functionally characterized. Mono‐ and dimethylation activity on l ‐tryptophan was reconstituted in vitro, whereas tryptamine was rejected as a substrate. Therefore, we describe a second l ‐tryptophan‐dependent pathway in Psilocybe that is not part of the biosynthesis of psilocybin. TrpM is unrelated to PsiM but originates from a retained ancient duplication event of a portion of the egtDB gene that encodes an ergothioneine biosynthesis enzyme. During mushroom evolution, this duplicated gene was widely lost but re‐evolved sporadically and independently in various genera. We propose a new secondary metabolism evolvability mechanism, in which weakly selected genes are retained through preservation in a widely distributed, conserved pathway.