What is "gamma-amanitin"

gamma-Amanitin or γ-amanitin is a Cyclic peptide of eight amino acids. It is an amatoxin, a group of toxins isolated from and found in several members of the Amanita genus of mushrooms, one being the Death cap ( Amanita phalloides) as well as the Destroying angel, a complex of similar species, principally A. virosa and A. bisporigera.