Antifreeze glycopeptides and peptides in Antarctic fish species from the Weddell Sea and the Lazarev Sea

Abstract

Antifreeze glycopeptides and peptides have been isolated from 37 species of Antarctic fish representing the families Nototheniidae, Artedidraconidae, Bathydraconidae, Channichthyidae, Muraenolepididae, Lipraididae, Zoarcidae and Myctophidae. Amino acid and carbohydrate analysis as well as antifreeze activity indicate that all investigated notothenioids contain antifreeze glycopeptides (AFGP). Pleuragramma antarcticum, Lepidonotothen kempi, Bathydraco marri and Dolloidraco longedorsalis synthesize additional antifreeze molecules. The non-notothenioid species possess antifreeze peptides (AFP), except Muraenolepis marmoratus and Macrourus holotrachys, which possess a glycosylated antifreeze peptide similar to the AFGP found in the notothenioid species. A novel glycopeptide comprised of the carbohydrate residue N-acetylglucosamine and the amino acids asparagine, glutamine, glycine, alanine, and traces of arginine, valine, leucine and threonine was isolated and characterized from P. antarcticum. The level of antifreeze concentration was dependent on the ambient water temperature, the depth of catch and life cycle of the species. Antifreeze activity of AFGP varies between 0.52 (Neopagetopsis ionah) and 1.20°C. (P. antarcticum) at a concentration of 20 mg ml-1. Antifreeze activity of AFP is lower than 0.50°C. A linear increase in activity of the AFGP could be demonstrated concomitant with decreasing ice content. The structural diversity of antifreeze molecules and their occurrence in a wide range of Arctic and Antarctic fish species suggest that they evolved from precursor proteins before the continental drift and recently during Cenozoic glaciation into the various antifreeze molecules.