MICROCYSTIN LR DEGRADATION BY PSEUDOMONAS-AERUGINOSA ALKALINE PROTEASE

We isolated several species of bacteria from the surface water of a Ja panese lake. Of the isolated bacteria, Pseudomonas aeruginosa was the only species which could degrade microcystin LR in vitro. Microcystin LR decreased to 4.5% of the spiked microcystin LR quantity in the P. a eruginosa culture, and was metabolized to (2S, 3S, 8S)-3-amino-2, 6, 8 -trimethyl-10-ehenyldeca-4E, 6E-dienoic acid (DmADDA). It was possible that P. aeruginosa hydrolysed nucleophilically the peptide bond of mi crocystin LR. We examined if pyochelin, pyocyanin and alkaline proteas e produced by P. aeruginosa affected the reduction of microcystin LR. In the result, DmADDA was produced from microcystin LR in the presence of 100 mu M H2O2 and 100 mu Meach of pyochelin, pyocyanin or both. Ho wever, the production of DmADDA was slight(2 to 12 mole%). After treat ment with P. aeruginosa alkaline protease, DmADDA was produced 75 mole % from microcystin LR. Therefore, we concluded that microcystin was de graded mainly by the action of P. aeruginosa alkaline protease. (C) 19 97 Elsevier Science Ltd.