Microcystin-LR
chemical compound
Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria. It is the most toxic of the microcystins.
Structure
Microcystins are cyclic heptapeptides. The seven amino acids that are involved in the structure of a microcystin include the unique amino acids ADDA and D-β-methyl-isoaspartate (D-β-Me-isoAsp). Furthermore, microcystins contain two variable residues, which make the differentiation between variants of microcystins. These two variable functionalities are always standard proteinogenic amino acids - In microcystin-LR these are leucine and arginine.
More than 250 microcystins have been identified to date, representing differences in the two variable residues and some modifications in the other amino acids. These modifications include demethylation of Masp and Mdha and methylesterification of D-Glu. Different microcystins have different toxicity profiles, with microcystin-LR found to be the most toxic.
Biosynthesis
Microcystins are small nonribosomal peptides.
“Microcystin-LR” enters the record as chemical compound. Crown Archives preserves that source wording while asking what Microcystin-LR, chemical and compound can confirm, complicate or overturn.
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The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Sep 12, 2026. The linked authority identifier is Q6839436. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Microcystin-LR” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.