What is "beta-amanitin"

beta-Amanitin or β-amanitin is a cyclic peptide comprising eight amino acids. It is part of a group of toxins called amatoxins, which can be found in several mushrooms belonging to the Amanita genus. Some examples are the Death cap ( Amanita phalloides) and members of the Destroying angel complex, which includes A. virosa and A. bisporigera. Due to the presence of α-amanitin, β-amanitin, γ-amanitin and ε-amanitin these mushrooms are highly lethal to human beings.