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Amino Acid Composition of the Host-specific Toxin of Helminthosporium carbonum¹

^a Chemistry and Biology Research Institute, Research Branch, Canada Department of Agriculture, Ottawa, Ontario, Canada

The host-specific toxin of Helminthosporium carbonum (C₃₂H₅₀N₆O₁₀) was hydrolyzed by 6 N HCl to yield a number of -amino acids. The common amino acids, proline and alanine, occurred in a ratio of 1:2. Two other unstable -amino acids that produced lower color values with ninhydrin were also produced. One of these was tentatively identified as 2-amino-2,3-dehydro-3-methylpentanoic acid by electrolytic reduction to isoleucine. Additional ninhydrin-reacting substances were produced in low yield and probably represented secondary hydrolysis products of the unstable amino acids. The finding of an ,-unsaturated linkage in H. carbonum toxin explains the instability of the compound and may also account for its specific toxicity.