The structure of polymyxin S. (Studies on antibiotics from the genus Bacillus. XXI)

Amino acid analysis on the acid hydrolyzate of polymyxin S1 revealed its amino acid composition. Isolation of the constituent amino acids and measurement of their optical activities clarified their chiralities: Dab(5L), Thr(3L), Ser(1D) and Phe(1D). The constituent fatty acid was identified with anteisononanoic acid by gas chromatography and mass spectrometry. By the action of polymyxin acylase, deacyl polymyxin S was obtained. Successive EDMAN degradation reaction on deacyl polymyxin S revealed the amino acid sequence. Further evidence for the structure of polymyxin S1 was obtained by partial acid hydrolysis on tetra-(DNP)-polymyxin S1.