title: Evidence for a covalently bound form of microcystin-LR in salmon liver and Dungeness crab larvae.
abstract: The chemically unique nature of the C20 beta-amino acid (2S,3S,8S,9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6- dienoic acid (Adda) portion of the microcystins has been exploited to develop a strategy to analyze for the total microcystin-LR (1; see Figure 1) burden in salmon liver and crab larvae tissues. Lemieux oxidation of microcystin-LR (1) gives 2-methyl-3-methoxy-4-phenylbutanoic acid (2), a unique marker for the presence of microcystins. The butanoic acid 2 can be isolated and detected by GC/MS from the livers of Atlantic salmon that received an ip injection of microcystin-LR (1) and from tissues of wild-caught crab larvae. The Lemieux oxidation-GC/MS results are compared with those from MeOH extraction-PPase analysis. Only approximately 24% of the total microcystin-LR (1) burden in salmon liver tissue is found to be extractable with MeOH. Similarly, the Lemieux oxidation-GC/MS method detected 10,000-fold greater microcystin concentrations in Cypress Island Dungeness crab larvae than did the MeOH extraction-PPase method. The disparity in microcystin concentrations measured by the two methods is taken as direct evidence for the existence of covalently bound microcystins in vivo.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, Canada.
authors.forename: D E
authors.initials: DE
authors.lastname: Williams
authors.forename: M
authors.initials: M
authors.lastname: Craig
authors.forename: T L
authors.initials: TL
authors.lastname: McCready
authors.forename: S C
authors.initials: SC
authors.lastname: Dawe
authors.forename: M L
authors.initials: ML
authors.lastname: Kent
authors.forename: C F
authors.initials: CF
authors.lastname: Holmes
authors.forename: R J
authors.initials: RJ
authors.lastname: Andersen
mesh_terms: D000818:Animals; D003386:Brachyura / Q000196:embryology; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D007814:Larva / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008387:Marine Toxins / Q000378:metabolism* / Q000494:pharmacology; D052998:Microcystins; D010456:Peptides, Cyclic / Q000378:metabolism* / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D012474:Salmon
chemical_list: D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR