Amanullin

Amanullin is a cyclic peptide. It is an amatoxin, all of which are found in several members of the mushroom genus "Amanita". The oral of amanullin is approximately 20 mg/kg in mice; however, it is non-toxic in humans.
Toxicology.
Like other amatoxins, amanullin is an inhibitor of RNA polymerase II. Amanullin has a species dependent and specific attraction to the enzyme RNA polymerase II. Upon ingestion, it binds to the RNA polymerase II enzyme, effectively causing cytolysis of hepatocytes (liver cells).