Amanita Ocreata - Toxicity

Toxicity

Amanita ocreata is highly toxic, and has been responsible for a number of mushroom poisonings in western North America, particularly in the spring. It contains highly toxic amatoxins, as well as phallotoxins, a feature shared with the closely related death cap (A. phalloides), half a cap of which can be enough to kill a human, and other species known as destroying angels. There is some evidence it may be the most toxic of all the North American phalloideae, as a higher proportion of people consuming it had organ damage and 40% perished. Dogs, too, have been known to consume this fungus in California with fatal results.

Amatoxins consist of at least eight compounds with a similar structure, that of eight amino-acid rings; of those found in A. ocreata, α-amanitin is the most prevalent and along with β-amanitin is likely to be responsible for the toxic effects. The major toxic mechanism is the inhibition of RNA polymerase II, a vital enzyme in the synthesis of messenger RNA (mRNA), microRNA, and small nuclear RNA (snRNA). Without mRNA, essential protein synthesis and hence cell metabolism stop and the cell dies. The liver is the principal organ affected, as it is the first organ encountered after absorption by the gastrointestinal tract, though other organs, especially the kidneys, are susceptible to the toxins.

The phallotoxins consist of at least seven compounds, all of which have seven similar peptide rings. Although they are highly toxic to liver cells, phallotoxins have since been found to have little input into the destroying angel's toxicity as they are not absorbed through the gut. Furthermore, one phallotoxin, phalloidin, is also found in the edible (and sought-after) blusher (Amanita rubescens).