γ-Amanitin (gamma-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 mushroom genus Amanita, one being the death cap (Amanita phalloides) as well as the destroying angel, a complex of similar species, principally A. virosa and A. bisporigera. The compound is highly toxic, inhibits RNA polymerase II, disrupts synthesis of mRNA, and can be fatal.[1]
Amatoxins selectively inhibit Eukaryotic RNA polymerase II by tightly to the enzyme and severely inhibits translocation along the DNA template; thus the synthesis of mRNA and proteins stops.[2] Amatoxin consumption is characterized by a long asymptomatic period of a few hours (up to a day or more) followed by quick physiological decline due to acute hepatic and tubular necrosis.[3] γ-Amanitin has been found to have similar levels of toxicity to other amatoxins such as α-Amanitin.