Microcystine

Microcystin, sometimes written microcystine, refers to a family of hepatotoxic cyclic peptides produced by freshwater cyanobacteria such as Microcystis, Anabaena, and Planktothrix. These toxins are commonly released into water during cyanobacterial blooms and can persist in surface and drinking-water sources, especially when blooms decay.

Chemistry and variants: Microcystins are cyclic heptapeptides containing unusual amino acids, including the Adda moiety, which is essential for toxicity. More than 100 variants have been identified; the best studied are microcystin-LR, -RR, and -YR.

Mechanism: They inhibit serine/threonine protein phosphatases PP1 and PP2A, leading to hyperphosphorylation, hepatocellular injury, and, in severe cases, liver failure in animals and humans.

Exposure and health effects: Humans can be exposed via contaminated drinking water, recreational water, or consumption of fish and shellfish from affected waters. Acute exposure causes abdominal pain, vomiting, and liver dysfunction; chronic exposure is studied for potential carcinogenic risk and long-term liver effects.

Detection and regulation: Monitoring uses ELISA screening and LC-MS confirmation. Water-treatment strategies include coagulation, activated carbon, ozonation, and advanced oxidation to reduce microcystin levels. Regulatory limits for drinking water vary by country; public health agencies issue advisories during blooms and may set concentration thresholds to protect human and animal health.