Epsilon-Amanitin

Epsilon-Amanitin is a cyclic peptide of eight amino acids. It is an amatoxin, a group of toxins found in several members of the Amanita genus of mushrooms, most notably the deadly Amanita phalloides, also known as the death cap mushroom.

Structure and Biochemistry

Epsilon-Amanitin is structurally similar to other amatoxins, with a characteristic "cyclic" structure formed by a peptide bond between the amino group of the amino acid tryptophan and the carboxyl group of the amino acid glycine. This cyclic structure is crucial for the toxin's ability to resist degradation by enzymes and to bind to its target in the body, the RNA polymerase II enzyme.

The structure of epsilon-amanitin includes several unusual amino acids, including hydroxyproline, tryptathionine, and cysteine. These unusual amino acids contribute to the toxin's stability and potency.

Toxicity and Symptoms

Epsilon-Amanitin is highly toxic and is one of the main toxins responsible for the deadly effects of Amanita phalloides poisoning. It works by inhibiting the enzyme RNA polymerase II, which is essential for the synthesis of messenger RNA (mRNA), transfer RNA (tRNA), and small nuclear RNA (snRNA) in cells. This inhibition disrupts protein synthesis and leads to cell death.

Symptoms of epsilon-amanitin poisoning can take several hours to appear and typically include severe abdominal pain, vomiting, and diarrhea. This is followed by a period of apparent recovery, after which liver and kidney damage become apparent. Without treatment, death can occur within a week.

Treatment

There is no specific antidote for epsilon-amanitin, and treatment is primarily supportive, including hydration and correction of electrolyte imbalances. In severe cases, liver transplantation may be necessary.

See Also

• Amatoxin
• Amanita phalloides
• RNA polymerase II

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