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Amatoxins are a subgroup of at least eight toxic compounds found in several genera of poisonous mushrooms, most notably Amanita phalloides and several other members of the genus Amanita, as well as some Conocybe, Galerina and Lepiota mushroom species.
The compounds have a similar structure, that of eight amino-acid rings; they were isolated in 1941 by Heinrich O. Wieland and Rudolf Hallermayer of the University of Munich.[1] Of the amatoxins, α-amanitin is the chief component and along with β-amanitin is likely responsible for the toxic effects.[2][3] Their 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, grind to a halt and the cell dies.[4] The liver is the principal organ affected, as it is the organ which is first encountered after absorption in the gastrointestinal tract, though other organs, especially the kidneys, are susceptible.[5] The RNA polymerase of Amanita phalloides is insensitive to the effects of amatoxins; as such, the mushroom does not poison itself.[6]
Their swift intestinal absorption coupled with their thermostability explains why their toxic effects occur in a relatively short period of time. The most severe effects are toxic hepatitis with centrolobular necrosis and hepatic steatosis, as well as acute tubulointerstitial nephropathy, which altogether induce a severe hepatorenal syndrome (with a potentially fatal outcome). The estimated minimum lethal dose is 0.1 mg/kg or 7 mg of toxin in adults. There are eight amatoxins:
- alpha-amanitin
- beta-amanitin
- gamma-amanitin
- epsilon-amanitin
- amanullin
- amanullinic acid
- proamanullin
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Detection
Presence of amatoxins in mushroom samples may be detected by the Meixner Test (also know as the Wieland Test).
References
- ^ Litten, W. (March 1975). "The most poisonous mushrooms". Scientific American 232 (3): 90–101. PMID 1114308.
- ^ Köppel C (1993). "Clinical symptomatology and management of mushroom poisoning". Toxicon 31 (12): 1513–40. doi:. PMID 8146866.
- ^ Dart, RC (2004). "Mushrooms", Medical toxicology. Philadelphia: Williams & Wilkins, 1719–35. ISBN 0-7817-2845-2.
- ^ Karlson-Stiber C, Persson H (2003). "Cytotoxic fungi - an overview". Toxicon 42 (4): 339–49. doi:. PMID 14505933.
- ^ Benjamin.p217
- ^ Horgen, Paul A.; Allan C. Vaisius and Joseph F. Ammirati (1978). "The insensitivity of mushroom nuclear RNA polymerase activity to inhibition by amatoxins". Archives of Microbiology 118 (3): 317–9. doi:. PMID 567964.
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