Thaumatins protein

Thaumatin is a mixture of five thaumatin proteins thaumatins I, II, III, and a and b where thaumatins I and II predominate. Thaumatins I and II consist of almost identical sequences of amino acids. There are no unusual side-chains or peptide linkages, and there are no end-group substitutions. 

Thaumatin. Thaumatin [53850-34-3] is a mixture of proteins extracted from the fmit of a West African plant, Thaumatococcus daniellii (Beimett) Benth. Work at Unilever showed that the aqueous extract contains two principal proteins thaumatin I and thaumatin II. Thaumatin I, mol wt 22,209, contains 207 amino acids in a single chain that is cross-linked with eight disulfide bridges. Thaumatin II has the same number of amino acids, but there are five sequence differences. Production of thaumatins via genetic engineering technology has been reported (99). 

As a protein, thaumatin is remarkably water-soluble (up to 60%) and is stable to heat at low pH. It has been reported that a thaumatin solution at pH less than 5.5 can be heated at 100°C for several hours without loss of sweetness. Comprehensive reviews on thaumatin as sweetener are available (100,101). 

Singh, N.K., Bracket, C.A.S., Hasegawa, P.M., Handa, A.K., Bruckel, S., Hermondson, M.A., Pfankoch, E., Regnier, F.E. Bressan, R.A. (1987o). Characterisation of osmotin. A Thaumatin-like protein associated with osmotic adaptation in plant cells. Plant Physiology, 85, 528-36. 

That the initial event of taste stimulation takes place on the cell surface of the taste receptor is now universally accepted. In addition, accumulated evidence strongly suggests that taste-bud stimulation is extracellular in nature. For example, (1) the sweet-taste response is both rapid and reversible, (2) the intensely sweet proteins monellin" and thaumatin could not possibly penetrate the cell, because of their size, and (3) miraculin, the taste-modifying glycoprotein, having a molecular weight of 44,000 would also be too large to penetrate the taste cell. ... 

In a study of the three-dimensional structure of thaumatin, it was reported that, not only do antibodies raised against thaumatin cross-react with monellin,but antibodies raised against monellin also cross-react with thaumatin, suggesting that there is some structural similarity between portions of the two sweet-protein molecules. Earlier studies " had shown that there is a limited homology in the amino acid sequence in the two proteins. Five tripeptides in monellin have their counterparts in thaumatin. 

Other than the sweeteners discussed so far thaumatin is a polypeptide consisting of amino acids commonly found in food proteins. It is quickly and completely digested like proteins and did, after demonstration of its metabolic characteristics, only require a rather limited set of safety data. In contrast to the other intense sweeteners the ADI of thaumatin is not specified , as for substances of similar composition.27 It is approved in many countries but, owing to its flavour enhancing properties, is often used as a flavour enhancer rather than a sweetener. 

Thaumatin-like proteins provide a sweet taste in food. They may display antifungal activity and are treated as potential allergens. These proteins are found in strawberries, apples, bell peppers, and cherries (Scheurer et al., 1999 Aalberse et al., 2001). 

The design of safe sweeteners is very important for people who are afiected by diabetes, hyperlipemia, caries and other diseases that are linked to sugar consumption. Sweet proteins, which are found in several tropical plants, are many times (100-100,000) sweeter than sucrose on a molar basis. Only a few sweet proteins are known miraculin, monellin, thaumatin, curculin, mabinlin. 

Brazzein is another small sweet-tasting protein whose solution structure has been recently solved by NMR. Brazzein tastes 2000 times sweeter than sucrose on a weight basis and is exceptionally thermostable. As indicated by NMR, the structure of this 54 residue, single-chain polypeptide does not change between 32 and 82 °C and retains its sweetness after incubation at 98 °C for two hours.Brazzein contains one a-helix and three strands of antiparallel jd-sheet stabilized by four intramolecular disulphide bonds. It has been proposed that the disulphide bonds could be responsible for the thermostability of brazzein by forming a compact structure at the tertiary level.The structure of brazzein does not resemble that of the other two sweet proteins with known structures, monellin and thaumatin, whereas sequence alignment and structural prediction indicate that brazzein shares the fold of a newly identified family of serine proteinase inhibitors. 

There are seven known sweet and taste-modifying proteins, namely (1) monellin and (2) thaumatin (3) mabinlin. and (4) curculin (5) pentadin, (6) brazzein and (7) miraculin.The properties and characteristics of these proteins are illustrated in Table 2. There are several recent reviews relating to sweet proteins. Apart from curculin and... 

Source Adapted from Kurihara. " At least five different forms of thaumatin and four different forms of mabinlin have been identified. A chromatographic fraction containing a 12 kDa protein was sweet. This same fraction, when subjected to electrophoresis under nonreducing conditions showed bands in the region between 22 kDa and 41 kDa, su esting the presence of subunits. 

Hordenine Rt ° , Seedling Hordeum protein 26kDa Sd Hordeum protein 30kDa Sd Hordeum protein 32kDa Sd Hordeum thaumatin-like protein R Sd ° Hordeum thaumatin-like protein S Sd Hordeum vulgare protease inhibitor Fr °° Hordeum vulgare protein MW 28000 Sd w/o seedcoat ... 

Svendsen. Two antifungal thaumatin- HV019 like proteins from barley grain. FEBS Lett 1991 291(1) 127-131. 

Unusual proteins are also characteristic of the biome free-sulfydryl type for both tropical Americas and the East, and taste-modifying type, like miraculin, monellins, and thaumatin, for tropical Africa. 

Sweet Taste. The mechanism of sweetness perception has been extensively studied because of its commercial importance. Many substances that vary in chemical structure have been discovered which are similar to the taste of sucrose. Commercial sweeteners include sucralose, acesulfame-K, saccharin, aspartame, cyclamate (Canada) and the protein thaumatin 4), Each sweetener is unique in its perceived sensation because of the time to the onset of sweetness and to maximum sweetness, ability to mask other sensations, persistence, aftertaste and intensity relative to sucrose [TABLE IT. For example, the saccharides, sorbitol and... 

Figure 30-31 Structures of some very sweet compounds. The backbone structure of the protein thaumatin I is included. The main body of this structure consists of two (3 sheets forming a flattened (3 barrel. (3 Strands in the top sheet are shaded light, and those in the bottom sheet are darker. Open bars represent disulfide bonds, and the regions with sequences homologous to monellin are indicated by the hatched marks. From de Vos et al.9i0...

C Boy. Thaumatin—a taste modifying protein. Int Food Ingred 6 23-25, 1994. 

A Mackenzie, JB Pridham, NA Saunders. Changes in the sweet proteins (thaumatins) in Thaumato-coccus danielli fruits during development. Phytochem 24(11) 2503-2506, 1985. 

Cornelissen, B., Hooft van Huijsduijnen, R. Bol, J. (1986). A tobacco mosaic virus-induced tobacco protein is homologous to the sweet-tasting protein thaumatin. Nature 321, 531-2. 

Pierpoint, W., Tatham, A. Pappin, D. (1987). Identification of the virus-induced protein of tobacco leaves that resembles the sweet-protein thaumatin. Physiological and Molecular Plant Pathology 31, 291-8. 

Richardson, M., Valdes-Rodriguez, S. Blanco-Labra, A. (1987). A possible function for thaumatin and a TMV-induced protein suggested by homology to a maize inhibitor. Nature 327, 432-4. 

---