Structure–Activity Relationships of Anabaenopeptins as Carboxypeptidase and Phosphatase Inhibitors

Anabaenopeptins are a family of cyanobacterial cyclic peptides that display potent enzyme inhibition, particularly against carboxypeptidases A and B, as well as the serine/threonine phosphatases PP1 and PP2A. Defined by a 19-membered macrocyclic ring and a ureido-linked exocyclic amino acid, these compounds vary considerably in their amino acid composition, influencing both potency and selectivity. This review compiles published IC50 values for natural and synthetic anabaenopeptins, organizing them by enzyme target, and highlighting recurring structural motifs that drive inhibitory activity. Through this comparative analysis, we identify emerging trends in structure–activity relationships and underscore gaps in assay standardization and structural validation. These insights provide a critical foundation for advancing the biological evaluation of anabaenopeptins as environmental contaminants, mechanistic probes, and candidate scaffolds for therapeutic development.