Pentadin

Pentadin, a sweet-tasting protein, was discovered and isolated in 1989, in the fruit of oubli (Pentadiplandra brazzeana Baillon), 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.

Pentadin and brazzein were discovered in 1994, and are the 2 sweet-tasting proteins discovered in the African fruit, Pentadiplandra brazzeana. Pentadiplandra brazzeana consists of a red outer-shell that contains three to five seeds inside of it, which are covered by a layer of red pulp that contain brazzein and pentadin, sweet tasting proteins. Pentadiplandra brazzenna Baillon bears red berries that are about 2 inches in diameter and contain the sweet tasting proteins, Brazzein and Pentadin, as discussed above. Brazzein and Pentadin are extracted from the same fruit however Pentadin is extracted from the fruit after it is heat-dried and Brazzein is extracted from the fresh form of the fruit. The fruit has been consumed by the apes and the natives for a long time. The berries of the plant were incredibly sweet African locals call them "j'oublie" (French for "I forget") because their taste helps nursing infants forget their mothers' milk.

Sweet tasting proteins have been known to exist for many years and indigenous people have been known to use these proteins as a way to add sweetness to their foods without the use of other sweetening agents, such as sucrose. The sweetness of Pentadin has been estimated to be about 500 times more than Sucrose, when looked at on a weight basis.

The molecular weight of Pentadin is estimated to be 12kDa and has a sweetening ability of 500 times moe than sucrose. This sweet tasting protein is known to resemble monellin on a sweetness basis and is higher than thaumatin.

Pentadin is the second protein discovered in Oubli (Pentadiplandra brazzeana) and is similar to Brazzein, the first protein discovered from Pentadiplandra brazzeana. More structural analysis has been done on Brazzein than on Pentadin and it is difficult to understand the particular structure of Pentadin however, some of the structural properties of Brazzein can be applied to Pentadin. Brazzein contains two regions that are particularly critical for the sweetness of the protein, the N- and C- terminus of the protein, and a region of the protein that contains the flexible loop around Arg43. The exact properties for Pentadin are unknown, however we can apply particular regions of the N- and C- terminus regions to the structure of Pentadin as they are both derived from the same fruit(Pentadiplandra brazzeana).

There are six sweet-tasting proteins - pentadin, thaumatin, monellin, mabinlin, brazzein, and curculin - all of which are isolated from plants in tropical forests. These proteins show no similarities in a structural or homologous sequence aspect. All of these sweet tasting proteins have different molecular lengths, with no sequence homology and little to none structural homology. Efforts to identify structural similarities among sweet tasting proteins included using the 3D structures and DALI to find similarities. However only a vague resemblance was found for the three proteins tested, monellin, thaumatin, and brazzein. Brazzein and thaumatin invoke respinses in humans through the T1R2-T1R3 receptor and can be applied t Pentadin a Brazzein and Pentadin are similar to one another. These repsonses in the T1R2-T1R3 receptor are similar to the small molecular weight sweeteners that include popular sweeteners. Proteins cannot generally stimulate taste receptors like sugar normally does, however the identified sweet tasting proteins, such as monellin, thaumatin, pentadin, curculin, and mabinlin are able to interact with one's taste receptors to create a sweet taste. Very low concentrations of these sweet tasting proteins are required for them to interact with our receptors, therefore they are also known to be low calorie sweeteners.

Physical properties
The amino acid composition of pentadin contains:


 * Aspartic Acid
 * Glutamic Acid
 * Serine
 * Proline
 * Glycine
 * Alanine
 * Valine
 * Methionine
 * Isoleucine
 * Leucine
 * Tyrosine
 * Phenylalanine
 * Lysine
 * Arginine
 * Histidine

Studies that have been conducted on the electrophoretic profile of pentadin revealed the presence of subunits that were joined together by disulfide bonds in the mature protein structure. These studies were done with and without the presence of 2-mercaptoethanol. The more prevalent amino acids found in Pentadin are aspartic acid, glutamic acid, tyrosine, lysine, and proline, with proline being the most dominant amino acid. The structure of Pentadin consists of subunits that are coupled by disulfide bonds and it is soluble in water. Pentadin can also withstand temperatures of 100 °C when exposed to it for 5 hours. The strength of the protein remains the same when it is exposed to temperature at and below 100 °C for an extended period of time        (≤ 5 hours).

Uses
The six sweet-tasting proteins can be used as a natural low-calorie sweetener to replace certain sugars. They are also good for the response of insulin in people who are diabetic. Sweet tasting proteins can be used as naturally occurring low calorie sweeteners due to them having more sweetness and a lower calorie value than Sucrose. Pentadin is a naturally occurring form of a low-calorie sweetener and can be used as a substitute for commonly used sugars, such as sucrose, glucose, and fructose.

Growing interests in artificial sweeteners and sweet-tasting proteins
There is a growing interest surrounding low calorie sweeteners due to the average American consuming approximately 17 teaspoons of sugar on a daily basis. The recommended amount of sugar consumed for men is 9 teaspoons and 6 teaspoons for women and with these increased amounts of sugar consumption, numerous health issues increase (high blood pressure, cardiovascular diseases, and increased risk of obesity). Sweet tasting proteins are being introduced as alternatives to other forms of sweeetening agents because they are also known to contain health benefits.

There are two forms of sweeteners available: natural sweeteners and artificial (synthetic) sweeteners. Natural sweeteners are derived from plants and these include Brazzein, Pentadin, and Thaumatin. These compounds provide sweetness with little to no calories however the long term effects of these natural proteins have not been studied intensively to accurately determine the adverse effects that may be caused. Some researchers have identified that these naturally derived sweet tasting proteins may cause weight gain and insulin secretion when consumed for long periods of time.

A link between chronic diseases, such as cardiovascular diseases, diabetes, hypertension, and obesity and excessive sugar consumption has been developed over the years. Increased sugar consumption causes an increase in energy intake leading to increased weight gain and chronic diseases. Due to an association between sugar consumption and chronic diseases, it is important to understand that there are sugar substitutes that one can use. Many sugar substitutes are available in the market today, however more research is required to determine whether or not sweet proteins, such as Pentadin, are safe for human consumption over extended periods of time.

Sweet tasting proteins and taste modifying proteins, such as Pentadin and Miraculin, are being used as safer alternatives to normal table sugar due to their low caloric intake. All of these sweet tasting proteins are isolated from fruits and contain no unpleasant aftertaste, however the nature of these proteins don't allow for mass production like we can do with artificial sweeteners.