Microcystin

Microcystins—or cyanoginosins—are a class of cyanotoxins, which are toxins produced by cyanobacteria, sometimes known as blue-green algae. Over 250 different microcystins have been discovered so far, of which microcystin-LR is the most common. Chemically they are cyclic heptapeptides produced through nonribosomal peptide synthases.

Cyanobacteria can produce microcystins in large quantities during algal blooms which then pose a major threat to drinking and irrigation water supplies, and the environment at large.

Characteristics

Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria; primarily Microcystis aeruginosa but also other Microcystis, as well as members of the Planktothrix, Anabaena, Oscillatoria and Nostoc genera.

Microcystin-LR (i.e. X = leucine, Z = arginine) is the most toxic form of over 80 known toxic variants, and is also the most studied by chemists, pharmacologists, biologists, and ecologists. Microcystin-containing 'blooms' are a problem worldwide, including China, Brazil, Australia, South Africa, the United States and much of Europe. Hartebeespoort Dam in South Africa is one of the most contaminated sites in Africa, and possibly in the world.

Chemistry

Microcystins have a common structural framework of D-Ala1-X2-D-Masp3-Z4-Adda5-D-γ-Glu6-Mdha7, where X and Z are variable amino acids; the systematic name "microcystin-XZ" (MC-XZ in short) is then assigned based on the one letter codes (if available; longer codes otherwise) of the amino acids.