Brazzein is a sweet-tasting

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that occurs naturally in oubli (''Pentadiplandra brazzeana''), a fruit native to the Atlantic coastal areas of

Central Africa Central Africa (French language, French: ''Afrique centrale''; Spanish language, Spanish: ''África central''; Portuguese language, Portuguese: ''África Central'') is a subregion of the African continent comprising various countries accordin ...

. Brazzein was first isolated in 1994 by scientists at the

University of Wisconsin–Madison The University of Wisconsin–Madison (University of Wisconsin, Wisconsin, UW, UW–Madison, or simply Madison) is a public land-grant research university in Madison, Wisconsin, United States. It was founded in 1848 when Wisconsin achieved st ...

. It is roughly 500 to 2000 times sweeter than

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

. Brazzein is found in the extracellular region of oubli fruit, in the pulp tissue surrounding the seeds. After pentadin, discovered in 1989, brazzein is the second sweet-tasting protein discovered in the Oubli fruit. Like other sweet proteins discovered in plants, such as

monellin Monellin, a sweet protein, was discovered in 1969 in the fruit of the West African shrub known as serendipity berry ('' Dioscoreophyllum cumminsii''); it was first reported as a carbohydrate.GE Inglett, JF May. Serendipity berries - Source of a ...

and

thaumatin Thaumatin (also known as talin) is a low-calorie sweetener and taste modifier. The protein is often used primarily for its flavor-modifying properties and not exclusively as a sweetener. The thaumatins were first found as a mixture of protein ...

, brazzein is extremely sweet compared to commonly used sweeteners. The fruit tastes sweet to humans, monkeys, and

bonobos The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee (less often the dwarf chimpanzee or gracile chimpanzee), is an endangered great ape and one of the two species making up the genus ''Pan (genus), Pan'' (the other bei ...

, but

gorilla Gorillas are primarily herbivorous, terrestrial great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or five su ...

s have mutations in their sweetness receptors so that they do not find brazzein sweet, and they are not known to eat the fruit.

Traditional use

The Oubli plant (from which the protein was isolated) grows in

Gabon Gabon ( ; ), officially the Gabonese Republic (), is a country on the Atlantic coast of Central Africa, on the equator, bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo to the east and south, and ...

and

Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...

, where its fruit has been consumed by the

ape Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

s and local people for a long time. Due to brazzein and pentadin, the berries of the plant are incredibly sweet. Locals call them "Oubli" (French for "forgot") in their vernacular language because their taste is said to encourage nursing infants to forget their mother's milk, as once they eat them they are said to forget to come back to the village to see their mother.

Protein structure

The monomer protein, consisting of 54 amino acid residues, is the smallest of the sweet proteins with a molecular weight of 6.5

kDa The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. It is a non-SI unit accepted f ...

. The

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

sequence of brazzein, adapted from the

Swiss-Prot UniProt is a freely accessible database of protein sequence and functional information, many entries being derived from genome sequencing projects. It contains a large amount of information about the biological function of proteins derived from ...

biological database of protein, is as follows: UniProtKB/Swiss-Prot database entry #PP56552
/ref>'' The structure of brazzein was determined by proton

nuclear magnetic resonance Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a ...

(NMR) at a pH of 5.2 and 22 °C. Brazzein has four evenly spaced

disulfide bonds In chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups. In in ...

and no sulfhydryl groups. 3D analysis of brazzein showed one

alpha-helix An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of ...

and three strands of anti-parallel

beta sheet The beta sheet (β-sheet, also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gene ...

. This is not superficially similar to either of the other two sweet-tasting proteins,

and

. However, a recent 3D study shows that these three proteins possess similar "sweet fingers" believed to elicit the sweet taste. Residues 29–33 and 39–43, plus residue 36, as well as the C-terminus were found to be involved in the sweet taste of the protein. The charge of the protein also plays an important role in its interaction with the sweet

taste receptor A taste receptor or tastant is a type of cellular receptor that facilitates the sensation of taste. When food or other substances enter the mouth, molecules interact with saliva and are bound to taste receptors in the oral cavity and other locat ...

. Based on this knowledge a synthesised improved brazzein, called pGlu-1-brazzein, was reported to be twice as sweet as the natural counterpart.

Sweetness properties

On a weight basis, brazzein is 500 to 2000 times sweeter than sucrose, compared to 10% sucrose and 2% sucrose solution respectively. Its sweet perception is more similar to sucrose than that of thaumatin, with a clean sweet taste, lingering aftertaste, and slight delay (longer than aspartame) in an equi-sweet solution. Brazzein is stable over a broad pH range from 2.5 to 8 and heat stable at 98 °C for 2 hours.

As a sweetener

Brazzein represents an alternative to available low-calorie

sweetener A sweetener is a substance added to food or drink to impart the flavor of sweetness, either because it contains a type of sugar, or because it contains a sweet-tasting sugar substitute. Various natural non-sugar sweeteners (NSS) and artificial s ...

s. As a protein, it is safe for diabetics. It is also very soluble in water (>50 mg/mL). When blended with other sweeteners, such as

aspartame Aspartame is an artificial non-saccharide sweetener commonly used as a sugar substitute in foods and beverages. 200 times sweeter than sucrose, it is a methyl ester of the aspartic acid/phenylalanine dipeptide with brand names NutraSwe ...

and

stevia Stevia () is a sweet sugar substitute that is about 50 to 300 times sweetness, sweeter than sugar. It is extracted from the leaves of ''Stevia rebaudiana'', a plant native to areas of Paraguay and Brazil. The active compounds in stevia are ...

, brazzein reduces side aftertaste and complements their flavor. Its taste profile is closer to sucrose than other natural sweeteners (apart from

). Unlike other sweet-tasting proteins, it can withstand heat, making it more suitable for industrial food processing. Papers have been published showing it can be made in a laboratory using

peptide synthesis In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...

and recombinant proteins were successfully produced via

E. coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly foun ...

. The Texas companies Prodigene and Nectar Worldwide were among the licensees to use Wisconsin Alumni Research Foundation patents on brazzein, and genetically engineer it into maize. Brazzein then can be commercially extracted from the maize through ordinary milling. Approximately one ton of maize yields 1-2 kilograms of brazzein. It can also be engineered into plants like wheat to make pre-sweetened grains, e.g. for cereals. A company was formed to bring it to market as a sweetener in 2008, which initially said it would start selling the product by 2010 once it obtained agreement from the FDA that its brazzein was

generally recognized as safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...

(GRAS). In 2024, the brand Oobli received the first GRAS certification from the FDA, with no potential concerns for consumption being raised.

References

External links