Structural Analysis of New Syringopeptins by Tandem Mass Spectrometry

New syringopeptins SP(SC)-t and -2 were isolated from culture filtrates of phytopathogenic bacterium strain SCt of Pseudomonas syringae pv. syringae. These syringopeptins were composed of a β-hydroxy fatty acid, a long sequence of aliphatic amino acids, and a lactone moiety of eight amino acids. The amino acid sequences were deduced from a comparison of their tandem mass sepctra with those of known syringopeptins SP-22a and SP-25a. SP(SC)-l and SP(SC)-2 resembled SP-22a, but differed from the latter by 3 amino acids.