The Brockmann body of fish synthesizes and secretes insulin. The Brockmann body of Antarctic fish has been described anatomically and shown to contain insulin immunoreactive sites, however, the primary structure of an Antarctic fish insulin has yet to be reported. Insulin was isolated from the Brockmann bodies of the Antarctic perciform teleost, Dissostichus mawsoni. The peptide was purified to homogeneity by gel filtration and reversed-phase HPLC. Insulin-containing fractions were identified by radioimmunoassay using antisera raised against porcine insulin. Electrospray ionization-mass spectrometry determined the mass of the isolated product to be 5725.27 a.m.u. The amino acid composition and primary structure were determined for the pyridylethylated A- and B chains. The amino acid sequences of the A chain and B chain were H-Gly-Ile-Val-Glu-Gln-Cys-Cys-His-GIn-Pro10-Cys-Asn-Ile-Phe- Asp-Leu-GIn-Asn-Tyr-Cys20-Asn-OH and H-Ala-Pro-Gly-Pro-GIn-His-Leu-Cys-Gly- Ser10-His-Leu-Val-Asp-Ala-Leu-Tyr-Leu-Val-Cys20-Gly-Glu-Arg-Gly-Phe-Phe- Tyr-Asn-Pro-Lys30-OH, respectively. The primary structure of insulin from Antarctic fish is compared with known structures of insulin from other vertebrates.
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