Anabaenopeptin B

Anabaenopeptins are a highly diverse group of bioactive peptides produced by several genera of cyanobacteria such as Anabaena, Planktothrix, Microcystis and Nodularia. These peptides are commonly detected in cyanobacterial blooms along with the well known microcystins. Unique cyclic peptides where lysine is conserved in position 2 and cyclisation is achieved by linkage of the lysine to the C-terminal amino acid. In addition the side chain of a single amino acid is attached via a ureido bond. Bioactive peptides originally isolated from Anabaena flos-aquae NRC 525-17 where they were shown to be non-toxic in mice but had dose dependant relaxations in rat aortic preparations with endothelium precontracted with 0.1µM norpinephrine.
Anabaenopeptins inhibit protein phosphatase.