Glycoproteins, antifreeze

Feeney, R. E., Bnrcham, T. S., and Yeh, Y, 1986. Antifreeze glycoproteins from polar fish blood. Annual Review of Biophysical Chemistry 15 59-78. 

A unique family of O-linked glycoproteins permits fish to live in the icy seawater of the Arctic and Antarctic regions where water temperature may reach as low as — 1.9°C. Antifreeze glycoproteins (AFGPs) are found in the blood of nearly all Antarctic fish and at least five Arctic fish. These glycoproteins have the peptide structure... 

FIGURE 9.28 The structure of the repeating unit of antifreeze glycoproteins, a disac-... 

An exotic function of glycoproteins is to act as antifreezes. Specifically, a number of Antarctic fish live in water cooled to about -1.9°C, a temperature below the freezing point of water and below that where the blood, mostly water, of these fish is expected to freeze. Clearly, this would be a disaster for these fish. They are saved from this fate by antifreeze glycoproteins. These proteins contain about 50 repeats of the tripeptide Ala-Ala-Thr. To each of these threonine residues is hooked a specific disaccharide. 

Glycoproteins are needed as lubricants, and also function as protective agents of surfaces. The viscosity of mucins is due to the carbohydrate moiety.393 Some species of arctic fish contain an antifreeze glycoprotein that lowers the freezing point of their blood408 by preventing the lattice fonnation of water-ice clusters, a step that is a prerequisite... 

Hays LM, et al. Antifreeze glycoproteins inhibit leakage from liposomes during thermotropic phase transitions. Proc Natl Acad Sci USA 1996 93 6835-6840. 

Fish living in Arctic and Antarctic waters may encounter temperatures as low as -1.9°C. The freezing point depression provided by dissolved salts and proteins in the blood is insufficient to protect the fish from freezing. As winter approaches, they synthesize and accumulate in their blood serum a series of eight or more special antifreeze proteins.a d One type of antifreeze glycoprotein from winter flounder contains the following unit repeated 17-50 times. 

AGGPs Antifreeze glycoproteins (from winter flounder) BP/Shell (Edwards, 1994) ... 

Figure 7.39. The diversity of antifreeze proteins and antifreeze glycoproteins in marine fishes. Shown are the structures of four types of AFPs (I-IV) and the AFGP found in Antarctic notothenioids and Arctic cod. AFPs I-IV are shown as ribbon structures. The tripeptide repeat (-ala-ala-thr-) and carbohydrate moiety (galactosyl-lV-acetylgalactosamine) of AFGPs illustrate the key element of AFGP structures in noto-thenioid and Arctic cod.

Chen, L., A.L. DeVries, and C.-H. C. Cheng (1997a). Evolution of antifreeze glycoprotein gene from a trypsinogen gene in Antarctic notothenioid fish. Proc. Natl. Acad. Sci. USA 94 3811-3816. 

Antifreeze Glycoprotein Analogs Synthesis, In Vitro Testing, and Applications... 

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