EM49, a new peptide antibiotic. II. Chemical characterization.

Abstract

EM 49 is a new, broad-spectrum peptide antibiotic. The products of acid hydrolysis have been identified as 2, 4-diaminobutyric acid, leucine, phenylalanine, and a mixture consisting chiefly of C10- and C11-β-hydroxy fatty acids. The antibiotic is a tetraäcidic base, having four free amino groups, which have been identified as the γ-amino groups of 2, 4-diaminobutyric acid residues. The nonintegral quantities of leucine and phenylalanine and the mixture of fatty acid obtained by acid hydrolysis indicated that EM 49 is a mixture of closely related compounds. That this is so has been verified by the separation of EM 49 by ion-exchange chromatography into four distinct fractions. The analytical properties of the mixture are in good agreement with those predicted from the products of hydrolysis of the individual ion-exchange fractions. We conclude that EM 49 is a complex of cyclic, homodectic octapeptide antibiotics that are monoacylated with β-hydroxy fatty acids.