Dehydroalanyllysine: Identical Cooh-Terminal Structures in the Peptide Antibiotics Nisin and Subtilin

The recent finding of alpha,beta-unsaturated amino acid residues by Gross and Morrel in the polypeptide antibiotic nisin has stimulated a wider investigation of other antibiotic peptides, particularly those known to contain lanthionine. Subtilin is similar to nisin in that it polymerizes easily and contains lanthionine and beta-methyl lanthionine. Like nisin it was found to contain a carboxyl terminal dehydroalanyllysine sequence and to be split by the enzyme nisinase. An additional alpha,beta-unsaturated amino acid residue was shown to be present in subtilin by reaction with excess methyl mercaptoacetate and subsequent hydrolysis and amino acid analysis. Nisin contains three dehydropeptide residues.