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Introduction to Miraculin

Miracle? I think you mean Miraculin. Miraculin is a protein that is best known for its ability to deceive human taste buds into thinking sour or acidic food is sweet. This homodimeric glycoprotein was first identified in the West African native fruit, Synsepalum dulcificum (also known as “Miracle Fruit”), and exists in the pulp of the miracle fruit. Miraculin’s deceptive properties have been exploited by several companies as sugar substitutes. However, the American Food and Drug Administration banned the use of miraculin after labeling it as an additive ^[3] . This prevented its commercial use in the food industry.

Miraculin’s Structure

Miraculin is composed of 191 amino acid residues linked primarily by peptide bonds, having a molecular weight of about 28 kDa. Sarroch Theerasil et al ^[4] use HPLC profiles and SDS-PAGE analyses to prove this. Miraculin is a homodimer made by two chains that have two N-glycosylated Asn residues and are cross-linked through a disulfide bridge. Miraculin can also exist in a tetramer form.

Predictivley-modeled structure of miraculin

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Miraculin’s interactions with human tongue receptors

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Miraculin-Like Proteins (MLPs)

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Other Proteins with Function Similar to Miraculin

Although miraculin-like proteins have already been discussed, the title of being “like” miraculin comes from its structural identity to miraculin rather than its functional identity. Neoculin (also goes by the name “curculin”) is another protein that “tricks” tongue receptors into perceiving sour taste as sweet. This protein is native to the Malaysian fruit of Curculigo latifolia. Unlike miraculin, neoculin is not tasteless and instead has a sweet taste on its own. Like miraculin though, the active form of neoculin is heterodimer consisting of two moners that are connected through disulfide bridges . ^[5] Thaumatin is another protein with taste-modifying properties. Like miraculin, this protein is also extracted from a plant native to West Africa. Thaumatin is a sweet tasting-protein with the ability to enhance the tongue’s response to sweet taste by more than 100 fold ^[6].