Brazzein

Brazzein is a sweet-tasting protein extracted from the West African fruit of the climbing plant Oubli (Pentadiplandra brazzeana Baillon). It was first isolated as an enzyme by University of Wisconsin-Madison in 1994.^[1]

With pentadin, discovered in 1989, brazzein is the second sweet-tasting proteins discovered in this African’s fruit.^[2]

Like the other natural sweet-proteins such as monellin and thaumatin, it is highly sweet.^[3]

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Traditional use

The plant grows in Gabon and Cameroon, where 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 "Oubli" (French for "forgot") in theire vernacular language because their taste helps nursing infants forget their mother's milk^[4] as once they eat it they forget to come back to to the village to see their mother.^[5]

Protein structure

The monomer protein, consisting of 54 amino acid residues, is the smallest of the sweet proteins with a molecular weigh of 6.5 kDa.^[1]

QDKCKKVYEN YPVSKCQLAN QCNYDCKLDK HARSGECFYD EKRNLQCICD YCEY

Amino acids sequence of the sweet-tasting protein brazzein adapted from Swiss-Prot biological database of protein.^[6]

3D analysis of brazzein showed one alpha-helix and three strands of anti-parallel betasheet. It is not similar to of either of the other two sweet-tasting proteins, monellin and thaumatin.^[7]

However, a recent 3D study shows that these three proteins possess similar "sweet fingers" believed to elicit the sweet taste.^[8]

Residues 29–33 and 39–43, plus residue 36, as well as the C-terminus were found to be involved in the sweet tasting of the protein. The charge of the protein plays also an important role in its interaction with the sweet taste receptor.^[1]

Based on this knowledge a synthesised improved brazzein, called pGlu-1-brazzein, was reported to be twice sweet as the natural counterpart.^[9]

Sweetness properties

On weight basis, brazzein is 500 to 2000 times sweeter than sugar, compared to 10% sugar and 2% sugar solution respectively.^[7]

Its sweet perception is more similar to sucrose than that of thaumatin with a clean sweet taste with lingering aftertaste and with a slight delay longer than aspartame in an equi-sweet solution.^[10]

Brazzein is stable over a broad pH range from 2.5 to 8^[11] and heat stable at 98°C for 2 hours.^[1]

As a sweetener

Brazzein represents an excellent alternative to available low calorie sweeteners. As a can be protein it is safe for diabetics and very soluble in water (>50mg/ml).^[11]

When blended with other sweeteners, sweeteners such as aspartame and stevia, brazzein reduces side aftertaste, provides quantitative and qualitative synergy.^[12]

Unlike other natural sweeteners, apart from thaumatin, its sweet profile is closer to sucrose. Unlike other sweet-tasting proteins, it can withstand heat which make it suitable for any industrial food manufacture.^[13]

Increase interest of brazzein make it difficult to source naturally from Gabon, further more protein can be easily synthesised by a solid-phase method.^[7] Recombinant proteins were successfully produced via by E. Coli.^[14]

The Texas companies Prodigene and Nectar Worldwide were among the licensees to use Wisconsin Alumni Research Foundation patents on brazzein, and genetically engineer the enzyme into maize. Brazzein then can be commercially extracted from 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.^[13]

Brazzein controversy

Despite the fact that the sweet taste of the berries was well known in West Africa, the university claims that the sweet compound (brazzein) is its own invention and admit to no connection with the Gabon.^[15]

This fact, which involved appropriation of legal rights by means of patents over indigenous biomedical knowledge without compensation to the indigenous groups, is considered by GRAIN and Green Peace of an act of Biopiracy.^[16]

References

See also

• Curculin
• Mabinlin
• Miraculin
• Monellin
• Thaumatin