Role of Antifreezing Proteins in Fishes

Antifreeze proteins (AFP) and antifreeze glycoproteins (AFGP) comprise a structurally diverse class of proteins that have in common the ability to bind to ice and inhibit its growth. This action at the surface of ice in contact with a solution of AFP leads to a lowering of the freezing point (non-equilibrium) below the melting point, referred to as thermal hysteresis (in C). AFPs are incorporated within ice when it freezes because of their affinity for its surface. There, even in the frozen state, they inhibit the growth of large ice crystals at the expense of small ones (recrystallization inhibition), particularly when ice approaches the melt temperature and becomes more fluid. As a result of these beneficial properties, AFPs and AFGPs have been incorporated into the freeze-resistance or freeze-tolerance strategies of many organisms such as marine fishes, insects, plants and bacteria.