Polypeptide Toxins in Amanita Mushrooms:

All of the toxins found in the Amanita spp. mentioned in this poisonous plants list are peptides. The distribution of the peptides varies in the different parts of the mushroom, with the cap being the most deadly part. The amatoxins, phallotoxins, and virotoxins are found in A. bisporigera, A. ocreata, A. phalloides, A. phalloides var. alba, A. suballiacea, A. tenuifolia, A. virosa, and some other mushrooms. The phallolysins are a recently discovered group of toxins as yet only seen in A. phalloides. Ibotenic acid is found in A. cothurnata, A. muscaria var.formosa, A. muscaria var.muscaria, and A. pantherina.

  1. Amatoxins
  2. Phallotoxins
  3. Virotoxins
  4. Phallolysins
  5. Ibotenic acid/Muscimol


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  1. Amatoxins

    2. There are nine amatoxins:

    Amatoxins are solely responsible for fatal human poisonings. They are bicyclic octapeptides which are much more potent than any of the other toxins. The amatoxins are taken up by the liver where they begin to cause damage. They are then secreted by the bile into the blood where they are taken up by the liver again, causing a cycle of damage and excretion. In the liver, amatoxins inhibit RNA-polymerase II. The liver is slowly destroyed and is unable to repair itself due to the inactivation of the RNA-polymerase. Thus, the liver slowly dissolves with no hope of repair.

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  2. Phallotoxins

    3. There are seven naturally occurring phallotoxins:

    The phallotoxins are all derived from the same seven amino acid cyclic peptide backbone. There are two groups of phallotoxins, neutral and acidic. The neutral phallotoxins contain D-threonine, while the acidic ones contain beta-hydroxy-succinic acid.
    Phallotoxins destroy liver cells by disturbing the equilibrium of G-actin with F-actin, causing it to shift entirely to F-actin. This leads to numerous exvaginations on the liver cell's membrane which render the cell susceptible to deformity by low-pressure gradients, even those of the portal vein in vivo. This is folowed by loss of potassium ions and cytoplasmic enzymes which leads to depletion of ATP and glycogen causing the final downfall of the liver.

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  3. Virotoxins

    4. There are six virotoxins:

    Although they have the same toxicological effects as and appear to be derived from the phallotoxins, the virotoxins are monocyclic heptapeptides, not bicyclic peptides.

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  4. Phallolysins
    5. There are three phallolysins that are hemolytically active proteins, but, as previously stated, they are heat and acid labile and do not pose a threat to humans.
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  5. Ibotenic acid/Muscimol
    6. Ibotenic acid is an Excitatory Amino Acid (EAA) and muscimol is its derivative. These toxins act by mimicking the natural transmitters glutamic acid and aspartic acid on neurons in the central nervous system with specialized receptors for amino acids. These toxins may also cause selective death of neurons sensitive to EAAs.


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 This series of web pages was created by an undergraduate student at Cornell University for the AS625 class. All comments and suggestions are welcome.

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