Thaumatin family | |||||||||
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Identifiers | |||||||||
Symbol | Thaumatin | ||||||||
Pfam | PF00314 | ||||||||
InterPro | IPR001938 | ||||||||
SMART | SM00205 | ||||||||
PROSITE | PDOC00286 | ||||||||
SCOP2 | 1thu / SCOPe / SUPFAM | ||||||||
OPM superfamily | 168 | ||||||||
OPM protein | 1aun | ||||||||
CDD | cd09215 | ||||||||
Membranome | 1336 | ||||||||
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Thaumatin I | |||||||
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Identifiers | |||||||
Organism | |||||||
Symbol | Thm1 | ||||||
PDB | 1RQW | ||||||
UniProt | P02883 | ||||||
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Thaumatin II | |||||||
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Identifiers | |||||||
Organism | |||||||
Symbol | Thm2 | ||||||
PDB | 3wou | ||||||
UniProt | P02884 | ||||||
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Thaumatin (also known as talin) is a low-calorie sweetener and flavor modifier. The protein is often used primarily for its flavor-modifying properties and not exclusively as a sweetener. [3]
The thaumatins were first found as a mixture of proteins isolated from the katemfe fruit ( Thaumatococcus daniellii ) (Marantaceae) of West Africa. Although very sweet, thaumatin's taste is markedly different from sugar's. The sweetness of thaumatin builds very slowly. Perception lasts a long time, leaving a liquorice-like aftertaste at high concentrations. Thaumatin is highly water soluble, stable to heating, and stable under acidic conditions.
Thaumatin production is induced in katemfe in response to an attack upon the plant by viroid pathogens. Several members of the thaumatin protein family display significant in vitro inhibition of hyphal growth and sporulation by various fungi. The thaumatin protein is considered a prototype for a pathogen-response protein domain. This thaumatin domain has been found in species as diverse as rice and Caenorhabditis elegans . Thaumatins are pathogenesis-related (PR) proteins, which are induced by various agents ranging from ethylene to pathogens themselves, and are structurally diverse and ubiquitous in plants: [4] They include thaumatin, osmotin, tobacco major and minor PR proteins, alpha-amylase/trypsin inhibitor, and P21 and PWIR2 soybean and wheat leaf proteins. The proteins are involved in systematically-acquired stress resistance and stress responses in plants, although their precise role is unknown. [4] Thaumatin is an intensely sweet-tasting protein (on a molar basis about 100,000 times as sweet as sucrose [5] ) found in the fruit of the West African plant Thaumatococcus daniellii: it is induced by attack by viroids, which are single-stranded unencapsulated RNA molecules that do not code for protein. The thaumatin protein I consists of a single polypeptide chain of 207 residues.
Like other PR proteins, thaumatin is predicted to have a mainly beta structure, with a high content of beta-turns and little helix. [4] Tobacco cells exposed to gradually increased salt concentrations develop a greatly increased tolerance to salt, due to the expression of osmotin, [6] a member of the PR protein family. Wheat plants attacked by barley powdery mildew express a PR protein (PWIR2), which results in resistance against that infection. [7] The similarity between this PR protein and other PR proteins and the maize alpha-amylase/trypsin inhibitor has suggested that PR proteins may act as some form of inhibitor. [7]
Within West Africa, the katemfe fruit has been locally cultivated and used to flavour foods and beverages for some time. The fruit's seeds are encased in a membranous sac, or aril, that is the source of thaumatin. In the 1970s, Tate and Lyle began extracting thaumatin from the fruit. In 1990, researchers at Unilever reported the isolation and sequencing of the two principal proteins found in thaumatin, which they dubbed thaumatin I and thaumatin II. These researchers were also able to express thaumatin in genetically engineered bacteria.
Thaumatin has been approved as a sweetener in the European Union (E957), Israel, and Japan. In the United States, it is generally recognized as safe as a flavouring agent (FEMA GRAS 3732) but not as a sweetener.
Since thaumatin crystallizes very quickly and easily in the presence of tartrate ions, thaumatin-tartrate mixtures are frequently used as model systems to study protein crystallization. The solubility of thaumatin, its crystal habit, and mechanism of crystal formation are dependent upon the chirality of precipitant used. When crystallized with L- tartrate, thaumatin forms bipyramidal crystals and displays a solubility that increases with temperature; with D- and meso-tartrate, it forms stubby and prismatic crystals and displays a solubility that decreases with temperature. [9] This suggests control of precipitant chirality may be an important factor in protein crystallization in general.
As a food ingredient, thaumatin is considered to be safe for consumption. [10] [11] In a chewing gum production plant, thaumatin has been identified as an allergen. Switching from using powdered thaumatin to liquid thaumatin reduced symptoms among affected workers. Additionally, eliminating contact with powdered gum arabic (a known allergen) resulted in the disappearance of symptoms in all affected workers. [12]
Thaumatin interacts with human TAS1R3 receptor to produce a sweet taste. The interacting residues are specific to old world monkeys and apes (including humans); only these animals can perceive it as sweet. [13]
Potassium bitartrate, also known as potassium hydrogen tartrate, with formula KC4H5O6, is a chemical compound with a number of uses, including:
Monellin, a sweet protein, was discovered in 1969 in the fruit of the West African shrub known as serendipity berry ; it was first reported as a carbohydrate. The protein was named in 1972 after the Monell Chemical Senses Center in Philadelphia, U.S.A., where it was isolated and characterized.
Miraculin is a taste modifier, a glycoprotein extracted from the fruit of Synsepalum dulcificum. The berry, also known as the miracle fruit, was documented by explorer Chevalier des Marchais, who searched for many different fruits during a 1725 excursion to its native West Africa.
Sweetness is a basic taste most commonly perceived when eating foods rich in sugars. Sweet tastes are generally regarded as pleasurable. In addition to sugars like sucrose, many other chemical compounds are sweet, including aldehydes, ketones, and sugar alcohols. Some are sweet at very low concentrations, allowing their use as non-caloric sugar substitutes. Such non-sugar sweeteners include saccharin and aspartame. Other compounds, such as miraculin, may alter perception of sweetness itself.
Synsepalum dulcificum is a plant in the Sapotaceae family, native to tropical Africa. It is known for its berry that, when eaten, causes sour foods subsequently consumed to taste sweet. This effect is due to miraculin. Common names for this species and its berry include miracle fruit, miracle berry, miraculous berry, sweet berry, and in West Africa, where the species originates, agbayun, taami, asaa, and ledidi.
Brazzein is a protein found in the West African fruit of Oubli. It was first isolated by the University of Wisconsin–Madison in 1994.
A crystallization adjutant is a material used to promote crystallization, normally in a context where a material does not crystallize naturally from a pure solution.
Purple acid phosphatases (PAPs) (EC 3.1.3.2) are metalloenzymes that hydrolyse phosphate esters and anhydrides under acidic condition. In their oxidised form, PAPs in solution are purple in colour. This is due to the presence of a dinuclear iron centre, to which a tyrosine residue is connected via a charge transfer. This metallic centre is composed of Fe3+ and M, where M is Fe3+, Zn2+, Mg2+ or Mn2+. The conserved Fe3+ is stabilised in the ferric form, whereas M may undergo reduction. Upon treatment with mild reductants, PAPs are converted to their enzymatically active, pink form. Treatment with strong reducing agents dissociates the metallic ions, and renders the enzyme colourless and inactive.
Curculin or neoculin is a sweet protein that was discovered and isolated in 1990 from the fruit of Curculigo latifolia (Hypoxidaceae), a plant from Malaysia. Like miraculin, curculin exhibits taste-modifying activity; however, unlike miraculin, it also exhibits a sweet taste by itself. After consumption of curculin, water and sour solutions taste sweet. The plant is referred to locally as 'Lumbah' or 'Lemba'.
Gymnemic acids are a class of chemical compounds isolated from the leaves of Gymnema sylvestre (Asclepiadaceae). They are anti-sweet compounds, or sweetness inhibitors. After chewing the leaves, solutions sweetened with sugar taste like water.
Pentadin, a sweet-tasting protein, was discovered and isolated in 1989, in the fruit of oubli, a climbing shrub growing in some tropical countries of Africa. Sweet tasting proteins are often used in the treatment of diabetes, obesity, and other metabolic disorders that one can experience. These proteins are isolated from the pulp of various fruits, typically found in rain forests and are also used as low calorie sweeteners that can enhance and modify existing foods.
Mabinlins are sweet-tasting proteins extracted from the seed of mabinlang, a plant growing in Yunnan province of China. There are four homologues. Mabinlin-2 was first isolated in 1983 and characterised in 1993, and is the most extensively studied of the four. The other variants of mabinlin-1, -3 and -4 were discovered and characterised in 1994.
The enzyme cutinase is a member of the hydrolase family. It catalyzes the following reaction:
T1R2 - Taste receptor type 1 member 2 is a protein that in humans is encoded by the TAS1R2 gene.
Gurmarin is a 35-residue polypeptide from the Asclepiad vine Gymnema sylvestre (Gurmar). It has been utilized as a pharmacological tool in the study of sweet-taste transduction because of its ability to selectively inhibit the neural response to sweet taste in rats. This rat inhibition appears to have high specificity to sugar (sweetener) molecules like sucrose, glucose, and saccharin as well as the amino acid glycine. As a sweet-taste-suppressing protein, Gurmarin shows signs of being reversible in nature although having little to no effect on the sweet taste sensation in humans suggesting the protein is only active on rodent sweet taste receptors.
Thaumatococcus daniellii, also known as miracle fruit or miracle berry, is a plant species from tropical Africa of the Marantaceae family. It is a large, rhizomatous, flowering herb native to the rainforests of western Africa in Sierra Leone, southeast to Gabon and the Democratic Republic of the Congo. It is also an introduced species in Australia and Singapore.
Protein crystallization is the process of formation of a regular array of individual protein molecules stabilized by crystal contacts. If the crystal is sufficiently ordered, it will diffract. Some proteins naturally form crystalline arrays, like aquaporin in the lens of the eye.
Triflin is a cysteine-rich secretory protein (CRISP), which is excreted by the venom gland of the Habu snake. Triflin reduces high potassium-induced smooth muscle contraction, suggesting a blocking effect on L-type calcium channels.
Endo-polygalacturonase (EC 3.2.1.15, pectin depolymerase, pectolase, pectin hydrolase, and poly-α-1,4-galacturonide glycanohydrolase; systematic name (1→4)-α-D-galacturonan glycanohydrolase (endo-cleaving)) is an enzyme that hydrolyzes the α-1,4 glycosidic bonds between galacturonic acid residues:
Pathogenesis-related (PR) proteins are proteins produced in plants in the event of a pathogen attack. They are induced as part of systemic acquired resistance. Infections activate genes that produce PR proteins. Some of these proteins are antimicrobial, attacking molecules in the cell wall of a bacterium or fungus. Others may function as signals that spread “news” of the infection to nearby cells. Infections also stimulate the cross-linking of molecules in the cell wall and the deposition of lignin, responses that set up a local barricade that slows spread of the pathogen to other parts of the plant.