Amatoxin-type

Treat amatoxin-type poisoning as described below. 

Some of the naturally occurring amatoxins from the amanullin series do not contain a y-hydroxylated side chain of isoleucine and are nontoxic. Therefore, it has been concluded that, in contrast to the case for phallotoxins, the presence of such a group in the amatoxins is prerequisite for toxic activity. This type of hydroxyl group is located on the concave side of the 24-membered macrocycle in the three-dimensional molecular structure and is involved in binding to the RNA polymerase enzyme. The chemical effect of the amatoxin side chain and the contribution of every structural element to biological activity have been successfully investigated 107,114). 

Two major types of cyclic peptides have been isolated from Amanita species. Phallotoxins, such as phalloin (6), have seven amino acids in the ring, whereas, amatoxins [e.g., a-amanitin (7)], have eight (Fig. 14.3). Certain portions of the molecules are crucial for toxicity for example, in the amatoxin amanullin (8), elimination of a single hydroxyl group from one amino acid eliminates activity. However, generalizations about the effects of structure changes on toxicity cannot yet be made reliably. 

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