A Revised Model for Muscarine Biosynthesis Involving Lysine Trimethylation

l-(+)-Muscarine is a widespread fatal toxin produced by various mushrooms that pose a severe threat to human health when they are mistaken for edible species. Apart from a single 1970s study that assumed l-glutamate and pyruvate were the building blocks of this unusual quaternary amine, surprisingly little is known about the toxin's biogenesis. We used Collybia rivulosa (syn. Clitocybe rivulosa), a mushroom notorious for producing muscarine, as our model for stable isotope incorporation experime