Purification and structure of the host-specific toxin from Helminthosporiumcarbonum race 1

The host specific toxin from Helminthosporium carbonum race 1 was purified from culture filtrates by solvent extraction, gel filtration, and high pressure liquid chromatography. High resolution mass spectrometry of the purified toxin gave a MW of 436.2318 and an elemental composition C21H32N406. Amino acid analysis and proton and 13C-NMR indicated a peptide containing four amino acids. Their sequence was determined by gas chromatography mass spectrometry. Finally, digestion of the amino acids with D- and L-amino acid oxidases gave the complete structure cyclo[(L-2-amino-9, l0-epoxy-8-oxodecanoyl)-D-prolyl-L-alanyl-L-alanyl].