Proteins thaumatin

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). 

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...

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. 

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. 

Iyengar RB, Smits P, van der Oureraa F, et al. The complete amino-acid sequence of the sweet protein thaumatin. Eur J Biochem 1979 96 193-204. 

Higginbotham JD. Talin protein (thaumatin). In O Brien Nabors L, Gelardi RC, eds. Alternative Sweeteners. New York Marcel Dekker, 1986 103-134. 

FIGURE 3.1 Crystals of a variety of macromolecules. In (a), clusters of needle crystals of bacterial a amylase in (b), crystals of a protease from pineapple, in (c), a crystal of satellite tobacco mosaic virus and in (d), a crystal of the sweet protein thaumatin. 

Slootstra, J.W., De Geus, P., Haas, H., Verrips, C.T., and Meloen, R.H. (1995). Possible active site of the sweet-tasting protein thaumatin. Chem. Senses 20, 535-543. 

The perception of sweet taste can be elicited by a wide range of chemical compounds. Two naturally occurring sweet proteins, thaumatin and monellin, are derived from the fruits of two African plants called katemfe and... 

Thaumatin is a group of intensely sweet basic proteins isolated from the fruit of Thaumatococcus danielli (West African Katemfe fruit). It consists essentially of the proteins Thaumatin I and Thaumatin II. Thaumatin is a taste-modifying protein that functions as natural sweetener or flavor enhancer. Thaumatin is stable in aqueous solutions between pH 2.0 and 10 at room temperature. As occurs with aspartame it is nutritive, containing 4kcalg , but due to its intense sweetness, the amounts used are small enough for thaumatin to be considered and classified as a nonnutritive sweetener. Thaumatin is approved for a number of uses in UK, Japan, Australia, the EU, and in many other countries. In the USA, it is approved as a flavor enhancer. 

The fruit of Thaumatococcus daniellii contains two sweet proteins thaumatin I and II, with /sac,g 2000. There are also low amounts of three other sweet proteins (thaumatin a, b and c). The complete amino acid sequence and the conformation (Fig. 8.7 and 8.8) of thaumatin I, a peptide chain with 207 amino acid residues, has been established (Table 8.5). As a result of cross reactions with an anti-serum against monellin (cf. 8.8.4), sequence Y(57)FD in a j3-tum is regarded as the site of contact with the sweetness receptor. It corresponds to sequence Y(A13)ASD of monellin. 

---