Biosynthesis of the Amanita Cyclic Peptide Toxins

Abstract

To a scientist in 1986, the prospects of ever identifying the enzymatic pathway, much less the genes, involved in the biosynthesis of the Amanita peptide toxins must have seemed remote. The organisms are intractable to culture, the molecules are uniquely complex, gene cloning was in its infancy, and high-throughput genomic sequencing was not yet invented. Several indirect approaches to gain at least some insight into the pathway were attempted in the author's and other's laboratories in the first decade of the twenty-first century, including feeding radiolabeled amino acids to mushroom slices, in vitro assays for nonribosomal peptide synthetases (NRPSs) using the ATP/PPi exchange assay (Walton 1987), DNA hybridization with heterologous NRPS probes, and polymerase chain reaction (PCR) based on conserved motifs in NRPSs. All these attempts were unsuccessful.