Antifreeze Glycoproteins: Elucidation of the Structural Motifs That Are Essential for Antifreeze Activity

✍ Scribed by Yuki Tachibana; Garth L. Fletcher; Naoki Fujitani; Sakae Tsuda; Kenji Monde; Shin-Ichiro Nishimura

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 293 KB
• Volume: 116
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/ange.200353110

✦ Synopsis

Antifreeze proteins (AFPs) and glycoproteins (AFGPs) collectively abbreviated as AF(G)Ps are essential to the survival of many marine teleost fishes that reside in polar and subpolar waters where temperatures decline below the colligative freezing points of their body fluids. [1] Although the AF(G)Ps are markedly diverse in structure, they all function by binding to the surface of embryonic ice crystals to inhibit their growth. This binding results in a freezing point depression without an appreciable change in the melting point. The difference between the melting and freezing temperatures, termed thermal hysteresis (TH), is used to detect and quantify the antifreeze activity. In addition to effecting a thermal hysteresis, concentrated fish AF(G)Ps alter the morphology of the ice crystal into a hexagonal bipyramid. [2] The AFGPs isolated from fish blood plasma consist of repeating tripeptide units (Ala-Thr-Ala) n with a disaccharide moiety (Galb1-3GalNAca1-) attached to each threonyl residue. [3] They range in molecular mass from approximately 33 kDa (50 repeating units) to 2.6 kDa (four repeating units).