2 CLOSELY RELATED PEPTIDE TOXINS IN AXENICALLY GROWN MICROCYSTIS-AERUGINOSA PCC-7806

Two closely related peptide toxins from axenically grown Microcystis aeruginosa PCC 7806 were purified using molecular mass, charge and solubility as criteria. Water extracts of cells were applied to reversed phase C18 cartridges, and toxic fractions eluting between 20% and 100% methanol in water (vol/vol) were subjected to gel filtration. The fraction with an apparent Mr of about 1 kDa was further separated by analytical paper electrophoresis and preparative ion exchange chromatography. Acidic, ninhydrin-negative toxic material was finally purified by reversed phase high performance liquid chromatography yielding two distinct toxic peptides. The LD100 for mice was determined at 0.075 mg per kg body weight for each toxin. The major toxin (T17) with Mr 994 was composed of equimolar amounts of erythro-β-methyl-D-aspartic acid, D-glutamic acid, D-alanine, L-leucine, L-arginine, N-methyl dehydroalanine and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid (Adda). The other toxin (T16) with Mr 980 had an identical composition except for a replacement of erythro-β-methyl-D-aspartic acid by D-aspartic acid. Mass spectrometric data suggested cyclic linkage for both toxins. © 1990, Gustav Fischer Verlag, Stuttgart · New York. All rights reserved.