Alpha-Amanitin

Alpha-Amanitin is a cyclic peptide of eight amino acids. It is possibly the most deadly of all the amatoxins, toxins found in several species of the mushroom genus Amanita, one of the most recognizable being Amanita phalloides, otherwise known as the death cap.

Etymology

The term "Amanitin" derives from the genus name Amanita, from which the toxin is most commonly sourced. The prefix "Alpha-" is used to distinguish it from other similar toxins, such as Beta-Amanitin and Gamma-Amanitin.

Structure and Function

Alpha-Amanitin is a bicyclic octapeptide with a molecular weight of approximately 900 daltons. It is heat-stable and does not denature in boiling water. The toxin functions by inhibiting RNA polymerase II, a vital enzyme in the synthesis of messenger RNA (mRNA), micro RNA, and small nuclear RNA (snRNA). Without these molecules, essential protein synthesis and hence cell metabolism are disrupted, leading to cell death.

Toxicity

Alpha-Amanitin is highly toxic and is responsible for the majority of mushroom poisoning deaths. The lethal dose in humans is estimated to be about 0.1 mg/kg body weight and the main target organ is the liver. Symptoms of poisoning include severe abdominal pain, vomiting, and diarrhea, which may lead to dehydration and kidney failure. There is currently no known antidote for alpha-amanitin, and treatment is largely supportive.

Related Compounds

Other amatoxins include Beta-Amanitin, Gamma-Amanitin, and Epsilon-Amanitin. These toxins are similar in structure and function to alpha-amanitin, but differ in their specific toxicity and distribution among Amanita species.

See Also

• Amatoxin
• Amanita phalloides
• RNA polymerase II

References

Alpha-Amanitin Resources
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