L-Threonine is connected to L-valine via its hydroxy-group forming an ester bonding. The hexanoic acid residue is attached to the TV-terminal aspartic acid residue which is not a part of the ring structure. The isolation procedure of the four cyanopeptolins as well as structure elucidation are described. Amino acid analysis, GC/MSanalysis, FAB-MSand several NMRtechniques were used to reveal the structures.Cyanobacteria (blue green algae) commonly found in fresh and brackish waters are well known to produce a manifold spectrum of secondary metabolites belonging to different substance classes such as alkaloids, phenolic dilactones, polyketides, amides, sulfur compounds, macrolides and peptides1}. Their most abundant peptide metabolites are cyclic peptide hepatotoxins termed microcystins. They are produced by strains of several waterbloom-forming cyanobacteria mainly from the genus Microcystis and are responsible for worldwide animal poisoning. Besides these well investigated toxins little is knownabout other peptides or peptide-related compounds produced by cyanobacteria. The tricyclic depsipeptide microviridin consisting of 14 L-amino acids has been found in Microcystis viridis from a lake in Japan. The depsipeptide acts as a strong inhibitor of thyrosinase2). Majusculamide C, a cyclic depsipeptide that inhibits the growth of a number of fungal plant pathogens has been isolated from Lyngbya majuscula3). The cyanobacterium Anabaena sp. BQ-16-1 produces a chlorine-containing cyclic decapeptide named puwainaphycin C which shows cardioactivity4).Recently, a fungicidal decapeptide named calophycin has been isolated from Calothrixfusca5\ and a cytotoxic bistratamide-related cyclic peptide, called westiellamide, was identified in the terrestrial cyanobacterium Westiellopsis prolifera6\ From Microcystis sp. PCC7806, f W.
Cell walls of Microcystis sp. PCC 7806 were purified from cell homogenates by sucrose density centrifugation and Triton X-100 extraction. The outer membrane contained carotenoids, two major peptidoglycan-associated proteins (Mr 49,000 and 52,000), and lipopolysaccharide (LPS) as indicated by the presence of 3-hydroxy fatty acids (3-OH-14:0, 3-OH-16:0, 3-OH-18:0), 4-oxo-18:0 fatty acid, and GlcN as lipid A components in addition to rare O-methyl sugars (2-O-methyl-6-deoxyhexoses I and II). The peptidoglycan (A1 gamma-type) was found to be covalently linked to a wall polysaccharide composed of GlcN, ManN, Man, Glc, and phosphate.
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