The toxicity and enzyme activity of a chlorine and sulfate containing aeruginosin isolated from a non-microcystin-producing strain.

The toxicity of six different strains was examined in acute toxicity assays with the crustacean . The presence of toxicity in two strains could be explained by the occurrence of microcystins. The other four strains were not able to produce microcystins due to different mutations in the microcystin synthetase () gene cluster. In these strains, toxicity was attributed to the presence of chlorine and sulfate containing compounds. The main representative, called aeruginosin 828A, of such a compound in the strain 91/1 was isolated, and structure elucidation by 2D-NMR and MS methods revealed the presence of phenyllactic acid (), chloroleucine (), 2-carboxy-6-(4'-sulfo-xylosyl)-octahydroindole (), and 3-aminoethyl-1--amidino-Δ-3-pyrroline () residues. Aeruginosin 828A was found to be toxic for with a LC value of 22.4 µM, which is only slightly higher than the toxicity found for microcystins. Additionally, very potent inhibition values for thrombin (IC = 21.8 nM) and for trypsin (IC = 112 nM) have been determined for aeruginosin 828A. These data support the hypothesis that aeruginosins containing chlorine and sulfate groups, which were found in microcystin-deficient strains, can be considered as another class of toxins.