Antifreeze protein
Encyclopedia
Antifreeze proteins or ice structuring proteins (ISPs) refer to a class of polypeptides produced by certain vertebrates, plants, fungi and bacteria that permit their survival in subzero environments. AFPs bind to small ice crystals
to inhibit growth and recrystallization
of ice that would otherwise be fatal. There is also increasing evidence that AFPs interact with mammalian cell membranes to protect them from cold damage. This work suggests the involvement of AFPs in cold acclimatization
.
, AFPs do not lower freezing point in proportion to concentration. Rather, they work in a noncolligative manner. This allows them to act as an antifreeze at concentrations 1/300th to 1/500th of those of other dissolved solutes. This minimizes their effect on osmotic pressure
. The unusual capabilities of AFPs are attributed to their binding ability at specific ice crystal surfaces.
Thermal hysteresis is easily measured in the lab with a nanolitre osmometer. Different organisms have different values of thermal hysteresis. The maximum level of thermal hysteresis shown by fish AFP is approximately -1.5°C (2.7°F). However, insect antifreeze proteins are 10–30 times more active than any known fish protein. This is probably because insects encounter lower temperatures on land than the –1°C or –2°C that fish face in freezing waters. During the extreme winter months, the spruce budworm
can battle temperatures approaching –30°C and resist freezing, though the Alaskan beetle Upis ceramboides
can survive in a temperature of –60°C by using an antifreeze molecule that is not composed of proteins.
The rate of cooling can influence the thermal hysteresis value of AFPs. Rapid cooling can substantially decrease the nonequilibrium freezing point, and hence the thermal hysteresis value. This means organisms may not be able to adapt to their subzero environment if the temperature drops abruptly.
Freeze avoidant: These species are able to prevent their body fluids from freezing altogether. Generally, the AFP function may be overcome at extremely cold temperatures, leading to rapid ice growth and death.
Freeze tolerant: These species are able to survive body fluid freezing. Some freeze tolerant species are thought to use AFPs as cryoprotectants to prevent the damages of freezing, but not freezing altogether. The exact mechanism is still unknown. However, it is thought AFPs may inhibit recrystallization and stabilize cell membranes to prevent damage by ice. They may work in conjunction with protein ice nucleators (PINs) to control the rate of ice propagation following freezing.
Antifreeze glycoproteins or AFGPs are found in Antarctic notothenioids and northern cod. They are 2.6-3.3 kD.
Type I AFP is found in winter flounder
, longhorn sculpin and shorthorn sculpin
. It is the best documented AFP because it was the first to have its three dimensional structure determined. Type I AFP consists of a single, long, amphipathic alpha helix, about 3.3-4.5 kD in size. There are three faces to the 3D structure: the hydrophobic, hydrophilic, and Thr-Asx face.
Type I-hyp AFP (where hyp stands for hyperactive) are found in several righteye flounders. It is approximately 32 kD (two 17 kD dimeric molecules). The protein was isolated from the blood plasma of winter flounder. It is considerably better at depressing freezing temperature than most fish AFPs.
Type II AFPs are found in sea raven
, smelt and herring
. They are cysteine-rich globular proteins containing five disulfide bond
s.
Type III AFPs are found in Antarctic eelpout
. They exhibit similar overall hydrophobicity at ice binding surfaces to type I AFPs. They are approximately 6kD in size.
Type IV AFPs are found in longhorn sculpins. They are alpha helical proteins rich in glutamate and glutamine. This protein is approximately 12KDa in size and consists of a 4-helix bundle. Its only posttranslational modification is a pyroglutamate residue, a cyclized glutamine
residue at its N-terminus. Scientists at the University of Guelph in Canada are currently examining the role of this pyroglutame residue in the antifreeze activity of type IV AFP from the longhorn sculpin.
See also dehydrin
.
Tenebrio or Type V AFPs are found in beetles, whereas Dendroides or Choristoneura fumiferana AFPs are found in some Lepidoptera
.
. The diatom
s Fragilariopsis cylindrus and F. curta play a key role in polar sea ice communities, dominating the assemblages of both platelet layer and within pack ice. AFPs are widespread in these species, and the presence of AFP genes
as a multigene family indicates the importance of this group for the genus Fragilariopsis. AFPs identified in F. cylindrus belong to an AFP family which is represented in different taxa and can be found in other organisms related to sea ice (Colwellia spp., Navicula glaciei, Chaetoceros neogracile and Stephos longipes and Leucosporidium antarcticum) and Antarctic inland ice bacteria (Flavobacteriaceae
, as well as in cold-tolerant fungi (Typhula ishikariensis
, Lentinula edodes and Flammulina populicola.)
. There are two reasons why many types of AFPs are able to carry out the same function despite their diversity:
–inhibition mechanism. They adsorb to nonbasal planes of ice, inhibiting thermodynamically favored ice growth. The presence of a flat, rigid surface in some AFPs seems to facilitate its interaction with ice via Van der Waals force
surface complementarity.
programs (molecular dynamics
or the Monte Carlo method
).
residues to the oxygens along the
direction in ice lattice, subsequently stopping or retarding the growth of ice pyramidal planes so as to depress the freeze point.
The above mechanism can be used to elucidate the structure-function relationship of other antifreeze proteins with the following two common features:
. These two things are completely separate entities, and show loose similarity only in their function.
. The proteins are isolated from fish and replicated, on a larger scale, in yeast.
There is concern from organizations opposed to genetically modified organism
s (GMOs), arguing modified antifreeze proteins may cause inflammation. However, as stated, ISPs have been approved for human consumption following diligent tests. Intake of AFPs in diet is likely substantial in most northerly and temperate regions already. Given the known historic consumption of AFPs, it is safe to conclude their functional properties do not impart any toxicologic or allergenic effects in humans.
As well, the transgenic process of ISP production is widely used in society already. This is how mass amounts of insulin
are made to treat people with type I diabetes each year. The process does not impact the product; it merely makes production more efficient and prevents the death of many fish who would, otherwise, be killed for the extraction of such protein.
Currently, Unilever
incorporates AFPs into some of its American products, including some popsicle
s and a new line of Breyers
Light Double Churned ice cream bars. In ice cream, AFPs allow the production of very creamy, dense, reduced fat ice cream with fewer additives. They control ice crystal growth brought on by thawing on the loading dock or kitchen table which drastically reduces texture quality.
In November 2009, the Proceedings of the National Academy of Sciences
published the discovery of a molecule in an Alaskan beetle that behaves like AFPs, but is composed of saccharide
s and fatty acid
s.
A 2010 study demonstrated the stability of superheated water ice crystals in an AFP solution, showing while the proteins can inhibit freezing, they can also inhibit melting.
Ice crystals
Ice crystals are a small crystalline form of ice including hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. The highly symmetric shapes are due to depositional growth, namely, direct deposition of water vapour onto the ice crystal...
to inhibit growth and recrystallization
Crystallization
Crystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...
of ice that would otherwise be fatal. There is also increasing evidence that AFPs interact with mammalian cell membranes to protect them from cold damage. This work suggests the involvement of AFPs in cold acclimatization
Acclimatization
Acclimatisation or acclimation is the process of an individual organism adjusting to a gradual change in its environment, allowing it to maintain performance across a range of environmental conditions...
.
Non-colligative properties
Unlike the widely used automotive antifreeze, ethylene glycolEthylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
, AFPs do not lower freezing point in proportion to concentration. Rather, they work in a noncolligative manner. This allows them to act as an antifreeze at concentrations 1/300th to 1/500th of those of other dissolved solutes. This minimizes their effect on osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....
. The unusual capabilities of AFPs are attributed to their binding ability at specific ice crystal surfaces.
Thermal hysteresis
AFPs create a difference between the melting point and freezing point known as thermal hysteresis. The addition of AFPs at the interface between solid ice and liquid water inhibits the thermodynamically favored growth of the ice crystal. Ice growth is kinetically inhibited by the AFPs covering the water-accessible surfaces of ice.Thermal hysteresis is easily measured in the lab with a nanolitre osmometer. Different organisms have different values of thermal hysteresis. The maximum level of thermal hysteresis shown by fish AFP is approximately -1.5°C (2.7°F). However, insect antifreeze proteins are 10–30 times more active than any known fish protein. This is probably because insects encounter lower temperatures on land than the –1°C or –2°C that fish face in freezing waters. During the extreme winter months, the spruce budworm
Spruce Budworm
Spruce budworms and relatives are a group of closely related insects in the genus Choristoneura. Most are serious pests of conifers. There are nearly a dozen Choristoneura species, subspecies, or forms, with a complexity of variation among populations found throughout much of the United States and...
can battle temperatures approaching –30°C and resist freezing, though the Alaskan beetle Upis ceramboides
Xylomannan
Xylomannan is a newly discovered antifreeze molecule, found in the freeze-tolerant Alaskan beetle Upis ceramboides. Unlike antifreeze proteins, xylomannanis not a protein. Instead, it is a combination of a sugar and a fatty acid that is found in cell membranes. As such is expected to work in a...
can survive in a temperature of –60°C by using an antifreeze molecule that is not composed of proteins.
The rate of cooling can influence the thermal hysteresis value of AFPs. Rapid cooling can substantially decrease the nonequilibrium freezing point, and hence the thermal hysteresis value. This means organisms may not be able to adapt to their subzero environment if the temperature drops abruptly.
Freeze tolerance versus freeze avoidance
Species containing AFPs may be classified as:Freeze avoidant: These species are able to prevent their body fluids from freezing altogether. Generally, the AFP function may be overcome at extremely cold temperatures, leading to rapid ice growth and death.
Freeze tolerant: These species are able to survive body fluid freezing. Some freeze tolerant species are thought to use AFPs as cryoprotectants to prevent the damages of freezing, but not freezing altogether. The exact mechanism is still unknown. However, it is thought AFPs may inhibit recrystallization and stabilize cell membranes to prevent damage by ice. They may work in conjunction with protein ice nucleators (PINs) to control the rate of ice propagation following freezing.
Fish AFPs
Type I AFP is found in winter flounder
Winter flounder
The winter flounder, Pseudopleuronectes americanus, is a right-eyed flatfish of the family Pleuronectidae. It is native to coastal waters of the western north Atlantic coast, from Labrador, Canada to Georgia, United States...
, longhorn sculpin and shorthorn sculpin
Sculpin
A Sculpin is a fish that belongs to the order Scorpaeniformes, suborder Cottoidei and superfamily Cottoidea, that contains 11 families, 149 genera, and 756 species...
. It is the best documented AFP because it was the first to have its three dimensional structure determined. Type I AFP consists of a single, long, amphipathic alpha helix, about 3.3-4.5 kD in size. There are three faces to the 3D structure: the hydrophobic, hydrophilic, and Thr-Asx face.
Type I-hyp AFP (where hyp stands for hyperactive) are found in several righteye flounders. It is approximately 32 kD (two 17 kD dimeric molecules). The protein was isolated from the blood plasma of winter flounder. It is considerably better at depressing freezing temperature than most fish AFPs.
Type II AFPs are found in sea raven
Sea raven
Sea ravens are a family, Hemitripteridae of scorpaeniform fishes. They are bottom-dwelling fishes that feed on small invertebrates, found in the northwest Atlantic and north Pacific oceans...
, smelt and herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
. They are cysteine-rich globular proteins containing five disulfide bond
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...
s.
Type III AFPs are found in Antarctic eelpout
Eelpout
The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance, with elongate bodies, and the dorsal and anal fins continuous with the caudal fin. All of the approximately 220 species are marine, mostly bottom-dwelling, some at great...
. They exhibit similar overall hydrophobicity at ice binding surfaces to type I AFPs. They are approximately 6kD in size.
Type IV AFPs are found in longhorn sculpins. They are alpha helical proteins rich in glutamate and glutamine. This protein is approximately 12KDa in size and consists of a 4-helix bundle. Its only posttranslational modification is a pyroglutamate residue, a cyclized glutamine
Glutamine
Glutamine is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders...
residue at its N-terminus. Scientists at the University of Guelph in Canada are currently examining the role of this pyroglutame residue in the antifreeze activity of type IV AFP from the longhorn sculpin.
Plant AFPs
The classification of AFPs became more complicated when antifreeze proteins from plant were discovered. Plant AFPs are rather different from the other AFPs in the following aspects:- They have much weaker thermal hysteresis activity when compared to other AFPs.
- Their physiological function is likely in inhibiting the recrystallization of ice rather than in the preventing ice formation.
- Most of them are evolved pathogenesisPathogenesisThe pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...
-related proteins, sometimes retaining antifungalFungicideFungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
properties.
See also dehydrin
Dehydrin
Dehydrins are a family of proteins present in plants that are produced in response to low temperatures and drought stress. They may do this through protecting membranes from damage. Their production is induced by ABA and in response to salt. Dehydrins in barley and maize are extremely hydrophilic...
Insect AFPs
There are two types of insect antifreeze proteins, Tenebrio and Dendroides AFPs which are both in different insect families. They are similar to one another, both being hyperactive (i.e. greater thermal hysteresis value) and consist of varying numbers of 12- or 13-mer repeats of approximately 8.3 to 12.5 kD. Throughout the length of the protein, at least every sixth residue is a cysteineCysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
.
Tenebrio or Type V AFPs are found in beetles, whereas Dendroides or Choristoneura fumiferana AFPs are found in some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
.
Sea ice organisms AFPs
AFPs were also found in microorganisms living in sea iceSea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
. The diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s Fragilariopsis cylindrus and F. curta play a key role in polar sea ice communities, dominating the assemblages of both platelet layer and within pack ice. AFPs are widespread in these species, and the presence of AFP genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
as a multigene family indicates the importance of this group for the genus Fragilariopsis. AFPs identified in F. cylindrus belong to an AFP family which is represented in different taxa and can be found in other organisms related to sea ice (Colwellia spp., Navicula glaciei, Chaetoceros neogracile and Stephos longipes and Leucosporidium antarcticum) and Antarctic inland ice bacteria (Flavobacteriaceae
Flavobacteriaceae
The family Flavobacteriaceae is composed of environmental bacteria. Most species are aerobic, some are microaerobic to anaerobic, for example Ornithobacterium, Capnocytophaga and Coenonia....
, as well as in cold-tolerant fungi (Typhula ishikariensis
Typhula ishikariensis
Typhula ishikariensis is, along with Typhula incarnata, the causal agent of Grey Snow Mould , a plant pathogen that can destroy turfgrass when covered for a long perioid with snow. It is a particular problem on golf courses established in unsuitable areas...
, Lentinula edodes and Flammulina populicola.)
Evolution
The remarkable diversity and distribution of AFPs suggest the different types evolved recently in response to sea level glaciation occurring 1-2 million years ago in the Northern hemisphere and 10-30 million years ago in Antarctica. This independent development of similar adaptations is referred to as convergent evolutionConvergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
. There are two reasons why many types of AFPs are able to carry out the same function despite their diversity:
- Although ice is uniformly composed of oxygen and hydrogen, it has many different surfaces exposed for binding. Different types of AFPs may interact with different surfaces.
- Although the five types of AFPs differ in their primary sequence of amino acids, when each folds into a functioning protein, they may share similarities in their three dimensional or tertiary structureTertiary structureIn biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...
that facilitates the same interactions with ice.
Mechanisms of action
AFPs are thought to inhibit growth by an adsorptionAdsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
–inhibition mechanism. They adsorb to nonbasal planes of ice, inhibiting thermodynamically favored ice growth. The presence of a flat, rigid surface in some AFPs seems to facilitate its interaction with ice via Van der Waals force
Van der Waals force
In physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...
surface complementarity.
Binding to ice
Normally, ice crystals grown in solution only exhibit the basal (0001) and prism faces (1010), and appear as round and flat discs. However, it appears the presence of AFPs exposes other faces. It now appears the ice surface 2021 is the preferred binding surface, at least for AFP type I. Through studies on type I AFP, ice and AFP were initially thought to interact through hydrogen bonding (Raymond and DeVries, 1977). However, when parts of the protein thought to facilitate this hydrogen bonding were mutated, the hypothesized decrease in antifreeze activity was not observed. Recent data suggest hydrophobic interactions could be the main contributor. It is difficult to discern the exact mechanism of binding because of the complex water-ice interface. Currently, attempts to uncover the precise mechanism are being made through use of molecular modellingMolecular modelling
Molecular modelling encompasses all theoretical methods and computational techniques used to model or mimic the behaviour of molecules. The techniques are used in the fields of computational chemistry, computational biology and materials science for studying molecular systems ranging from small...
programs (molecular dynamics
Molecular dynamics
Molecular dynamics is a computer simulation of physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a period of time, giving a view of the motion of the atoms...
or the Monte Carlo method
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...
).
Binding mechanism and antifreeze function
According to the structure and function study on the antifreeze protein from the fish winter flounder, the antifreeze mechanism of the type-I AFP molecule was shown to be due to the binding to an ice nucleation structure in a zipper-like fashion through hydrogen bonding of the hydroxyl groups of its four ThrThreonine
Threonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...
residues to the oxygens along the
direction in ice lattice, subsequently stopping or retarding the growth of ice pyramidal planes so as to depress the freeze point.The above mechanism can be used to elucidate the structure-function relationship of other antifreeze proteins with the following two common features:
- recurrence of a ThrThreonineThreonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...
residue (or any other polar amino acid residue whose side-chain can form a hydrogen bond with water) in an 11-amino-acid period along the sequence concerned, and - a high percentage of an AlaAlanineAlanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
residue component therein.
History
In the 1950s, Canadian scientist Scholander set out to explain how Arctic fish can survive in water colder than the freezing point of their blood. His experiments led him to believe there was “antifreeze” in the blood of Arctic fish. Then in the late 1960s, animal biologist Arthur DeVries was able to isolate the antifreeze protein through his investigation of Antarctic fish. These proteins were later called antifreeze glycoproteins (AFGPs) or antifreeze glycopeptides to distinguish them from newly discovered nonglycoprotein biological antifreeze agents (AFPs). DeVries worked with Robert Feeney (1970) to characterize the chemical and physical properties of antifreeze proteins. In 1992, Griffith et al. documented their discovery of AFP in winter rye leaves. Around the same time, Urrutia, Duman and Knight (1992) documented thermal hysteresis protein in angiosperms. The next year, Duman and Olsen noted AFPs had also been discovered in over 23 species of angiosperms, including ones eaten by humans. As well, they reported their presence in fungi and bacteria.Name change
Recent attempts have been made to relabel antifreeze proteins as ice structuring proteins to more accurately represent their function and to dispose of any assumed negative relation between AFPs and automotive antifreeze, ethylene glycolEthylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
. These two things are completely separate entities, and show loose similarity only in their function.
Commercial applications
Commercially, there appear to be countless applications for antifreeze proteins. Numerous fields would be able to benefit from the protection of tissue damage by freezing. Businesses are currently investigating the use of these proteins in:- increasing freeze tolerance of crop plants and extending the harvest season in cooler climates
- improving farm fish production in cooler climates
- lengthening shelf life of frozen foods
- improving cryosurgeryCryosurgeryCryosurgery is the application of extreme cold to destroy abnormal or diseased tissue. The term comes from the Greek words cryo and surgery meaning "hand work" or "handiwork"....
- enhancing preservation of tissues for transplant or transfusion in medicine
- therapy for hypothermia
Recent news
One recent, successful business endeavor has been the introduction of AFPs into ice cream and yogurt products. This ingredient, labelled ice-structuring protein, has been approved by the Food and Drug AdministrationFood and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
. The proteins are isolated from fish and replicated, on a larger scale, in yeast.
There is concern from organizations opposed to genetically modified organism
Genetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
s (GMOs), arguing modified antifreeze proteins may cause inflammation. However, as stated, ISPs have been approved for human consumption following diligent tests. Intake of AFPs in diet is likely substantial in most northerly and temperate regions already. Given the known historic consumption of AFPs, it is safe to conclude their functional properties do not impart any toxicologic or allergenic effects in humans.
As well, the transgenic process of ISP production is widely used in society already. This is how mass amounts of insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
are made to treat people with type I diabetes each year. The process does not impact the product; it merely makes production more efficient and prevents the death of many fish who would, otherwise, be killed for the extraction of such protein.
Currently, Unilever
Unilever
Unilever is a British-Dutch multinational corporation that owns many of the world's consumer product brands in foods, beverages, cleaning agents and personal care products....
incorporates AFPs into some of its American products, including some popsicle
Popsicle
Popsicle is the most popular brand of ice pop in the United States and Canada. The first ice pop was created by accident in 1905 when 11-year-old Frank Epperson left a cup of soda on his porch in cold weather overnight. The next morning he went to go get the soda and it was frozen, so he put two...
s and a new line of Breyers
Breyers
Breyers is a brand of frozen dessert and ice cream owned by Unilever . They have a large plant in the town of Framingham, Massachusetts, outside Boston....
Light Double Churned ice cream bars. In ice cream, AFPs allow the production of very creamy, dense, reduced fat ice cream with fewer additives. They control ice crystal growth brought on by thawing on the loading dock or kitchen table which drastically reduces texture quality.
In November 2009, the Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences...
published the discovery of a molecule in an Alaskan beetle that behaves like AFPs, but is composed of saccharide
Disaccharide
A disaccharide or biose is the carbohydrate formed when two monosaccharides undergo a condensation reaction which involves the elimination of a small molecule, such as water, from the functional groups only. Like monosaccharides, disaccharides form an aqueous solution when dissolved in water...
s and fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
s.
A 2010 study demonstrated the stability of superheated water ice crystals in an AFP solution, showing while the proteins can inhibit freezing, they can also inhibit melting.