[D-Leu(1)] microcystin-LR, a new microcystin isoplated from waterbloom in a Canadian prairie lake.
A previously undescribed cyclic heptapeptide hepatotoxin was isolated from a cyanobacteria waterbloom collected in Pakowki Lake, Alberta, Canada (49 degrees 20'N and 110 degrees 55'W). The compound was characterized by amino acid analysis, ESIMS/CID/MS, (1)H and (13)C NMR, and UV spectroscopy. Structure of the new microcystin was assigned as [D-Leu(1)]microcystin-LR (1). The amino acid composition is the same as microcystin-LR (2) except for D-Leu and L-Leu in 1 instead of D-Ala and L-Leu in 2. This is the first microcystin identified, among the 64 known microcystins, that has both a D- and L-Leu amino acid. Toxicity as measured by the protein phosphatase inhibition activity of 1 is similar to microcystin-LR. The presence of microcystins in waterblooms from this lake is discussed in relation to the almost yearly bird mortalities that have occurred there since 1995.
Park
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Department of Environmental Sciences, Faculty of Science, Shinshu University, Matsumoto 390-8621, Japan.
Namikoshi
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Brittain
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SM
Carmichael
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WW
Murphy
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T
D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay; D005618:Fresh Water / Q000382:microbiology; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D052998:Microcystins; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000737:chemistry / Q000302:isolation & purification*
C420867:Leu(1)microcystin-LR; D052998:Microcystins; D010456:Peptides, Cyclic