Xylocandin: A new complex of antifungal peptides II. Structural studies and chemical modifications

Abstract

Xylocandins A1, A2, B1, B2, C1, C2, D1 and D2are new antifungal peptides isolated from Pseudomonas cepacia ATCC 39277. The molecular weights of the xylocandins were deter-mined by fast atom bombardment mass spectrometry (A1 m/z 1,215; A21,199; B1 1,229; B21,213; C1 1,097; C21,081; D1 1,083; D21,067). Each xylocandin is a cyclic peptide con-taining glycine (1), serine (2), asparagine (1–3 residues), β-hydroxytyrosine (1), and an unusual amino acid with the formula C18H37NO5 (1). Additionally A1, A2, D1 and D2contain 2,4-diaminobutyric acid (1); A1, B1, C1 and D1 contain erythro-β-hydroxyasparagine (1); and A1, A2, B1 and B2contain xylose (1). For each xylocandin pair, an erythro-β-hydroxyasparagine residue in the first component of the pair is thus replaced by an asparagine in the second com-ponent, accounting for the 16 dalton mass difference for each pair. Chemical modification of A1 and A2 at the diaminobutyric acid and β-hydroxytyrosine residues was used to probe structural requirements for activity. © 1987, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.