Beta-Amanitin

Beta-Amanitin is a deadly amatoxin, a group of toxins found in several species of the mushroom genus Amanita. The principal species is Amanita phalloides, commonly known as the death cap. Beta-Amanitin is also found in Amanita ocreata and Amanita verna.

Etymology

The term "Amanitin" derives from the genus name Amanita, the group of mushrooms where this toxin is predominantly found. The prefix "Beta" is used to differentiate it from other similar toxins, such as alpha-Amanitin.

Structure and Biochemistry

Beta-Amanitin is a cyclic peptide of eight amino acids. It is a bicyclic octapeptide with a molecular weight of 900.6 Da. It is soluble in water, moderately soluble in methanol, and practically insoluble in methylene chloride.

Toxicity

Beta-Amanitin works by inhibiting RNA polymerase II, a vital enzyme in the synthesis of messenger RNA (mRNA), microRNA, and small nuclear RNA (snRNA). Without these molecules, protein synthesis and hence cell metabolism stop and the cell dies.

Symptoms and Treatment

The symptoms of beta-Amanitin poisoning are typically delayed for 6 to 24 hours after ingestion, leading to a false sense of recovery. Initial symptoms include severe abdominal pain, vomiting, and profuse watery diarrhea which may lead to dehydration and kidney failure. If left untreated, coma and death can occur within a week.

Treatment for beta-Amanitin poisoning is primarily supportive, with aggressive fluid and electrolyte replacement. Activated charcoal may be used to absorb the toxin if the patient presents within an hour of ingestion, but efficacy is unproven. There is no specific antidote for beta-Amanitin.

See Also

• Alpha-Amanitin
• Amatoxin
• Amanita phalloides
• Amanita ocreata
• Amanita verna

Beta-Amanitin Resources
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