Evidence for a covalently bound form of microcystin-LR in salmon liver and Dungeness crab larvae.
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.
Williams
D E
DE
Department of Chemistry, University of British Columbia, Vancouver, Canada.
Craig
M
M
McCready
T L
TL
Dawe
S C
SC
Kent
M L
ML
Holmes
C F
CF
Andersen
R J
RJ
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
D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR