[ALA4]SURFACTIN, A NOVEL ISOFORM FROM BACILLUS-SUBTILIS STUDIED BY MASS AND NMR SPECTROSCOPIES

When Bacillus subtilis S 499 was grown on a culture medium containing L-alanine as nitrogen source, a mixture of surfactins was obtained. Su itable chromatographic conditions allowed the separation of isoforms. Among these compounds, a new variant of surfactin was isolated and its structure was established by chemical and spectrometric methods, espe cially by NMR spectrometry. It contains a peptide sequence which diffe rs from that of standard surfactin by the replacement of the L-valine residue by L-alanine residue in position 4. The folding mode of [Ala4] surfactin as deduced from NMR results was compared with that of standa rd surfactin and the structure/properties relationship issuing from th e study of this new isoform is discussed.