Amino Acid Composition of the Host-specific Toxin of Helminthosporium carbonum.

The host-specific toxin of Helminthosporium carbonum (C(32)H(50)N(6)O(10)) was hydrolyzed by 6 n HCl to yield a number of alpha-amino acids. The common amino acids, proline and alanine, occurred in a ratio of 1:2. Two other unstable alpha-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 alpha,beta-unsaturated linkage in H. carbonum toxin explains the instability of the compound and may also account for its specific toxicity.