New anabaenopeptins, potent carboxypeptidase-A inhibitors from the cyanobacterium Aphanizomenon flos-aquae

Anabaenopeptins I (1) and J (2), two new ureido bond-containing cyclic peptides, were isolated from the cultured cyanobacterium Aphanizomenon flos-aquae (NIES-81) as potent carboxypeptidase-A (CPA) inhibitors. The gross structures of 1 and 2 were established by spectroscopic analysis, including the 2D NMR techniques. The absolute configurations of 1 and 2 were determined by spectral and chemical methods. Anabaenopeptins I and J inhibited CPA with IC(50) values of 5.2 and 7.6 ng/mL, respectively.

Occurrence and identification of UDP-N-acetylmuramyl-pentapeptide from the cyanobacterium Anabaena cylindrica

UDP-N-acetylmuramyl-pentapeptide (UDP-MurNAc-pentapeptide) is well known to be a key intermediate of bacterial peptidoglycan biosynthesis. We first detected the occurrence of UDP-MurNAc-pentapeptide in the cyanobacterium Anabaena cylindrica (NIES-19), and identified the structure of this pentapeptide by two-dimensional 1H-1H and 1H-13C NMR correlation experiments and mass spectra.

Aeruginosin 103-A, a thrombin inhibitor from the cyanobacterium Microcystis viridis

Aeruginosin 103-A was isolated from the cultured freshwater cyanobacterium Microcystis viridis(NIES-103). Its structure was elucidated to be 1 on the basis of 2D NMR data. This linear peptide inhibited thrombin, with an IC50 of 9.0 microgram/mL.

Dehydroradiosumin, a trypsin inhibitor from the cyanobacterium Anabaena cylindrica

Dehydroradiosumin, a novel potent trypsin inhibitory dipeptide, was isolated from the freshwater cyanobacterium Anabaena cylindrica (NIES-19). Its structure was elucidated as 1 on the basis of 2D NMR data and chemical degradation. The IC50 of 1 against trypsin was 0.1 microg/mL.