ADDA—the abbreviation for (all-S,all-E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid—is an unusual, but natural, amino acid. It is one of three amino acids (the others are leucine and arginine) found in microcystin-LR, one of several extremely toxic compounds produced by cyanobacteria.
Microcystin-LR was in the news this past summer because it is the most toxic of three microcystins detected in Toledo (OH)’s drinking water supply. This finding caused authorities to ban drinking the water for 3 days while the water treatment plant took measures to remove the toxins from the water. One of the remedies, chlorination, oxidizes the ADDA double bonds and initiates the chemical breakdown of the microcystins.
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