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Iterative l ‐Tryptophan Methylation in Psilocybe Evolved by Subdomain Duplication
Author(s) -
Blei Felix,
Fricke Janis,
Wick Jonas,
Slot Jason C.,
Hoffmeister Dirk
Publication year - 2018
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201800336
Subject(s) - psilocybin , tryptamine , biochemistry , biosynthesis , tryptophan , enzyme , gene , biology , chemistry , amino acid , pharmacology , hallucinogen
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.