Further Characterization of Glycine-Containing Microcystins from the McMurdo Dry Valleys of Antarctica

• Published in: Toxins
• Main Authors: Jonathan Puddick, Michèle R. Prinsep, Susanna A. Wood, Stephen Craig Cary, David P. Hamilton, Patrick T. Holland
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2015
• Subjects: microcystin; Antarctica; amino acid analysis; mass spectrometry; thiol derivatization; Medicine; R; Antarctic; McMurdo Dry Valleys; The Antarctic; Antarc*
• Online Access: https://doi.org/10.3390/toxins7020493; https://doaj.org/article/a71dd67d15ae410fa049666f5d870756

Microcystins are hepatotoxic cyclic peptides produced by several cyanobacterial genera worldwide. In 2008, our research group identified eight new glycine-containing microcystin congeners in two hydro-terrestrial mat samples from the McMurdo Dry Valleys of Eastern Antarctica. During the present study, high-resolution mass spectrometry, amino acid analysis and micro-scale thiol derivatization were used to further elucidate their structures. The Antarctic microcystin congeners contained the rare substitution of the position-1 ᴅ-alanine for glycine, as well as the acetyl desmethyl modification of the position-5 Adda moiety (3S-amino-9S-methoxy-2S,6,8S-trimethyl-10-phenyldeca-4E,6E-dienoic acid). Amino acid analysis was used to determine the stereochemistry of several of the amino acids and conclusively demonstrated the presence of glycine in the microcystins. A recently developed thiol derivatization technique showed that each microcystin contained dehydrobutyrine in position-7 instead of the commonly observed N-methyl dehydroalanine.