Curculin

In 1974, a petition for affiimation of the GRAS status of miracle fmit was submitted by the Miralin Company, mainly based on the fact that miracle fmits have been consumed by humans since before 1958. In 1977, the petition was denied by the FDA. However, miraculin remains a research curiosity. Its stmcture was elucidated in 1989 (125). Another protein, curculin [151404-13-6] (126), has also been reported to exert a sweet-inducing activity similar to miraculin. 

Cuprous sulfide, 7 767 Curative levels, optimizing, 21 803—804 Curatives, in polychloroprene latex compounding, 19 858 Curculin, 24 246 Curdlan, 4 724t 20 577-578... 

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. 

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... 

Table 2. Comparison of Thaumatin, Monellin, Mabinlin, Pentadin, Brazzein, Curculin and Miraculin... 

Thaumatin Monellin Mabinlin Pentadin Brazzein Curculin Miraculin... 

Curculin which is extracted with 0.5 M sodium chloride from the fruits of Curculigo latifolia and purified by ammonium sulphate fractionation, CM-sepharose ion-exchange chromatography and gel filtration.The protein acts as a low calorie sweetener and has a maximum sweetness equal to 0.35 M of sucrose. In addition to its sweetness, curculin also has taste modifying abilities since water and sour substances elicit a sweet taste after consumption of curculin. Currently, there is no other protein that has both sweet taste and taste modifying abilities. 

The taste modifying activity of the protein remains unchanged when it is incubated at 50°C for 1 hour between pH 3 and 11. Curculin elicits a sweet taste. It is 20 000 times sweeter than sucrose on a molar basis and 550... 

Yamashita H,Theerasilp S, AiuchiT, NakayaK, Nakamura Y, Kurihara Y, Purification and complete amino acid sequence of a new type of sweet protein with taste-modifying activity, curculin, / o/ Chem 265(26) 15770-15775, 1990. 

Harada S, Otani H, Maeda S, Kai Y, Kasai N, Kurihara Y, Crystallization and preliminary X-ray diffraction studies of curculin. A new type of sweet protein having taste modifying action, J Mol Biol 238 286—287, 1994. 

Curculin (13kDa, 4 Cys, protein) Curculigo latfolia (Hypoxidaceae) [fruit] Sweet (modifies taste induces sweet taste)... 

Several plant-derived proteins have been reported previously as sweeteners, inclusive of curculin [103], mabinlin [104,105], monellin [28,106], pentadin [107], and thaumatin, with the latter compound already mentioned as having commercial use as a sweetener and flavor enhancer [22]. Recently, a sixth sweet protein of plant origin, brazzein, was isolated from the fruits of an African climbing vine, Pentadiplandra... 

There are several flavour modifiers which are of minor industrial importance at present. These include natural and synthetic substances. A selection is presented in Tab. 3.53. Studies aimed at using miraculin and curculin as low-calorie sweeteners are in progress [23]. 

Curculin The sweet taste of curculin disappears in a few minutes after holding it in the mouth. Then, water elicits the sweet taste again and black tea tastes like sweetened tea. In addition, curculin modifies sour into sweet taste (like miraculin). Sweet tasting protein (molecular weight 28,000) isolated from the fruits of Curculigo latefolia. 

Although not very numerous, sweet macromolecules, both natural (Morris, 1976) and synthetic (Zaffaroni, 1975), are crucial for an understanding of the mechanism of the sweet receptor. The best known among proteins with a very strong sweet taste are brazzein (Ming and HeUekant, 1994), monellin, and thaumatin (Kurihara, 1992). Figure 5 shows molecular models of these three proteins. Other two known sweet proteins are mabinlin (Kurihara, 1992) and hen egg white (HEW) lysozyme (Maehashi and Udaka, 1998), whereas miraculin and curculin, which taste sweet when combined with sour substances, can be better described as taste-modifier proteins (Kurihara, 1992). 

Suzuki, M., Kurimoto, E., Nirasawa, S., Masuda, Y., Hori, K., Kurihara, Y., Shimba, N., Kawai, M., Suzuki, E., and Kato, K. (2004). Recombinant curculin heterodimer exhibits taste-modifying and sweet-tasting activities. FEBS Lett. 573,135-138. 

A recent review by Kurlhara deals with structures and physiological action of sweetness-masking substances such as gymnemic acids, ziziphin, heat-stable sweet protein, mabinlins and taste converting protein from sourness to sweetness such as miraculins and curculins. 

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