AFPs, including antifreeze glycoproteins (AFGPs) are proteins found in fish, insects, plants, microorganisms, and other living things that exist in low-temperature environments.

These proteins lower the temperature at which an organism freezes and contribute to maintaining the organism’s life by preventing freezing and the recrystallization of ice crystals.

Antifreeze proteins bond strongly to the surface of innumerable microscopic ice crystals that form in water at the moment of freezing and suppress their growth. Normally, ice crystals that form in an aqueous solution grow from a disk into an elliptical shape, but antifreeze proteins adhere to the ice and change the shape of the ice crystals. Even if the temperature is lowered only slightly, the size of the ice crystals remains nearly unchanged.

In addition, the AFPs inside fish have been observed as resulting in prolonged cell life, leading to the discovery that AFPs attach to the lipid bilayer membrane.