Co-Occurrence of Non-toxic (Cyanopeptolin) and Toxic (Microcystin) Peptides in a Bloom of Microcystis sp. from a Chilean Lake (original) (raw)

2000, Systematic and Applied Microbiology

A cyanobacterial bloom occurring in 1998 in lake Tres Pascualas (Concepci6n/Chile) was found to be dominated by Microcystis sp. The bloom contained both non-toxic (cyanopeptolin-type) and hepatotoxic (microcystin-type) peptides. Cyanopeptolin structure of the non-toxic peptides (called cyanopepto lin VW-l and VW-2, respectively) was revealed by matrix assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS) of whole cells, showing dominant molecular ions at mlz = 975 and mlz 995, respectively. On post source decay (PSD), both cyanopeptolins showed fragments deriving from Ahp-Phe-MTyr (3-amino-6-hydroxy-2-piperidone), the characteristic partial structure of cyanopeptolins. The amounts of each of the two cyanopeptolins could only roughly be estimated to be >0.1 % of bloom material dry weight. In addition the blooms contained microcystins (20 pg/g bloom dry weight as determined by RP-HPLC, 13 pg/g according to ELISA determination). MALDI-TOF-MS revealed several structural variants of microcystin: MCYST-RR (microcystin with Arg and Arg, indicated by mlz 1,038 and confirmed by PSD revealing a mlz = 135 fragment deriving from the Adda side chain, MCYST-FR (microcystin with Phe and Arg, indicated by mlz = 1,015). The presence of [ASp(31]-MCYST-LR (microcystin with Leu and Arg, Asp non-methylated, indicated by mlz 981), and [ASp(31]-MCYST-YR (microcystin with Tyr and Arg, Asp non-methylated, indicated by mlz 1,031) were likely. The relative amounts of the peptides varied between February, April, and May. Whole cell extracts from the bloom material revealed specific enzyme inhibitory activities. The serinproteases trypsin, plasmin, elastase were inhibited, assumable due to the cyanopeptolins found. Elastase and the cysteine-protease papain were not inhibited, inhibitions of protein kinase and glutathione Stransferase (GST) were low. Strong inhibition was observed with protein-phosphatase-1, likely due to the microcystins present in the samples.