Miraculin
Encyclopedia
Miraculin is a natural sugar substitute
, a glycoprotein
extracted from the fruit of Synsepalum dulcificum. The berry, which contains active polyphenol
s, was first documented by explorer Chevalier des Marchais
, who searched for many different fruits during a 1725 excursion to its native West Africa.
Miraculin itself is not sweet. However, after the taste buds are exposed to miraculin, ordinarily sour foods, such as citrus
, are perceived as sweet. This effect lasts up to an hour.
Miraculin works by binding to the sweet receptors on the tongue. Miraculin's effect lasts as long as the protein is bound to the tongue, which can be up to an hour. It makes most acidic foods taste sweet, but does not improve the taste of bitter things.
The active substance, isolated by Prof. Kenzo Kurihara (栗原 堅三 Kurihara Kenzō), a Japan
ese scientist, was named miraculin after the miracle fruit when Kurihara published his work in Science
in 1968.
s and some carbohydrate
chains.
Miraculin occurs as a tetramer (98.4 kDa), a combination of 4 monomers group by dimer. Within each dimer 2 miraculin glycoproteins are linked by a disulfide bridge.
The molecular weight of the glycoprotein is 24.6 kDa including 3.4 kDa (13.9% of the weight) of sugar constituted (on molar ratio) of glucosamine (31%), mannose (30%), fucose (22%), xylose (10%) and galactose (7%).
The taste modifying protein, miraculin, has seven cystein residues in a molecule composed of 191 amino acid residues. Both tetramer miraculin and native dimer miraculin in its crude state have the taste-modifying activity of turning sour tastes into sweet tastes.
(another taste-modifying agent), is not sweet by itself, but it can change a sour beverage into a sweet beverage, even for a long period after consumption. The anti-sweet compound, Gymnemic acid
suppresses the sweet taste of miraculin, like it does for sucrose
.
The duration and intensity of the taste-modifying phenomena depends on various factors — miraculin concentration, duration of contact of the miraculin with the tongue, and acid concentration. Maximum sweet-induced response has been shown to be equivalent to the sweetness of 17% sucrose solution.
Glycoprotein is sensitive to heat: when heated over 100 °C, miraculin loses its taste-modifying property. Miraculin activity is inactivated at pH below 3 and pH above 12 at room temperature. The sweet modifying effect stays at pH 4 (in acetate buffer), for 6 months at 5 °C.
The detailed mechanism of the taste-inducing behaviour is still unknown. It has been suggested that the miraculin protein can change the structure of taste cells on the tongue. As a result, the sweet receptors are activated by acids, which are sour in general. This effect remains until the taste bud
s return to normal. The two histidine
residues (i.e. His29 and His59) appear to be mainly responsible for the taste-modifiying behavior. One site maintains the attachment of the protein to the membranes while the other (with attached xylose
or arabinose
) activates the sweet receptor membrane in acid solutions.
Further research at the University of Tokyo using a system of cultured cells which allowed the testing of human taste receptors at various pH to uncover the mechanism.
As already known miraculin binds strongly to the sweet taste receptors on our tongues, however it does not activate receptors at neutral pH.
Once acid is introduced, the miraculin protein changes shape in such a way that it turns on the sweet receptors it is bound to, causing an ultra-sweet sensation without affecting other flavours tasted.
Once the acidic food is swallowed, miraculin returns to the inactive shape until the next acidic food comes along. This can continue for about an hour while it is still bound to the taste receptor.
http://news.discovery.com/human/miracle-fruit-berry-everything-taste-sweet-110926.html
in acidic food (e.g. soft drinks). Japan
ese researchers' more or less successful attempts to mass produce it are focused on recombinant technology. While attempts to express it in yeast
and tobacco plants have failed, researchers have succeeded in preparing genetically modified E. coli bacteria, lettuce
and tomatoes that express miraculin. The scientists' crops resulted in 40 microgram
s of miraculin per gram
of lettuce leaves, which was considered a large amount. Two grams of lettuce leaves produced roughly the same amount of miraculin as in one miracle fruit berry.
Miraculin was never approved for use as a sweetener by the United States Food and Drug Administration
(FDA). In the 1970s the Miralin Company planned on bringing miraculin to market and was founded with investments by Reynolds Metals
, Barclays, and Prudential
. Legal advice and contact with the FDA indicated that miraculin would be approved as generally recognized as safe
as the berries had been eaten for centuries in Africa with no reports of adverse reactions (substances used in food prior to January 1, 1958, through either scientific procedures or through experience based on common use in food can be designated GRAS). However, on the eve of the product's launch in 1974 the FDA determined that miraculin would be considered a food additive
and thus require years more testing. At this point the company's investment capital could not sustain them and Miralin folded. Afterward, Miralin requested the FDA documents under the freedom of information act. The documents were nearly completely blacked out, and the rationale for the sudden change in regulation was not revealed.
Miraculin has a novel food status in the European Union
. However it is approved in Japan
as a harmless additive
, according to the List of Existing Food Additives published by the Ministry of Health and Welfare (published by JETRO).
from heating, and thus miracle berries are not taste-bud active when cooked.
While miraculin changes the perception
of taste, it does not change the food's chemistry, leaving the mouth and stomach vulnerable to the high acid
ity of some foods, such as lemon juice
, that may cause irritation if eaten in large quantities.
Sugar substitute
A sugar substitute is a food additive that duplicates the effect of sugar in taste, usually with less food energy. Some sugar substitutes are natural and some are synthetic. Those that are not natural are, in general, called artificial sweeteners....
, a glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
extracted from the fruit of Synsepalum dulcificum. The berry, which contains active polyphenol
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
s, was first documented by explorer Chevalier des Marchais
Chevalier des Marchais
Reynaud Des Marchais, Chevalier des Marchais was a French cartographer and navigator who travelled extensively in the west coast of Africa, the West Indies and the northwest coast of South America between 1704 and 1727, under service to the King of France. His maps and manuscripts were published...
, who searched for many different fruits during a 1725 excursion to its native West Africa.
Miraculin itself is not sweet. However, after the taste buds are exposed to miraculin, ordinarily sour foods, such as citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
, are perceived as sweet. This effect lasts up to an hour.
Miraculin works by binding to the sweet receptors on the tongue. Miraculin's effect lasts as long as the protein is bound to the tongue, which can be up to an hour. It makes most acidic foods taste sweet, but does not improve the taste of bitter things.
The active substance, isolated by Prof. Kenzo Kurihara (栗原 堅三 Kurihara Kenzō), a Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese scientist, was named miraculin after the miracle fruit when Kurihara published his work in Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....
in 1968.
Glycoprotein structure
Miraculin was first sequenced in 1989 and was found to be a glycoprotein consisting of 191 amino acidAmino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s and some carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
chains.
Miraculin occurs as a tetramer (98.4 kDa), a combination of 4 monomers group by dimer. Within each dimer 2 miraculin glycoproteins are linked by a disulfide bridge.
SIGNAL (29) M MethionineMethionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
KLysineLysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
EGlutamic acidGlutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...
LLeucineLeucine is a branched-chain α-amino acid with the chemical formula HO2CCHCH2CH2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins...
TThreonineThreonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...
MLSSerineSerine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
LS FPhenylalaninePhenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
FFVValineValine is an α-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar...
SAAlanineAlanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
LLAA AANAsparagineAsparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side-chain's functional group. It is not an essential amino acid...
PProlineProline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
LLSAA1-50 D Aspartic acidAspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...
SAPNPVLDIIsoleucineIsoleucine is an α-amino acid with the chemical formula HO2CCHCHCH2CH3. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested. Its codons are AUU, AUC and AUA....
DGGlycineGlycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
EKLRArginineArginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
TGTN YTyrosineTyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
YIVPVLRDHHistidineHistidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
GGGLTVSATT PNGTFVCPPR51-100 VVQ GlutamineGlutamine is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders...
TRKEVDH DRPLAFFPEN PKEDVVRVST DLNINFSAFM PNPGPETISS101-150 W TryptophanTryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
CRWTSSTVW RLDKYDESTG QYFVTIGGVK FKIEEFCGSG FYKLVFCPTV151-191 CGSCKVKCGD VGIYIDQKGR GRRLALSDKP FAFEFNKTVY F Amino acids Proteinogenic amino acidProteinogenic amino acids are those amino acids that can be found in proteins and require cellular machinery coded for in the genetic code of any organism for their isolated production. There are 22 standard amino acids, but only 21 are found in eukaryotes. Of the 22, 20 are directly encoded by...
sequence of glycoprotein miraculin unit adapted from Swiss-Prot biological database of protein sequences.
The molecular weight of the glycoprotein is 24.6 kDa including 3.4 kDa (13.9% of the weight) of sugar constituted (on molar ratio) of glucosamine (31%), mannose (30%), fucose (22%), xylose (10%) and galactose (7%).
The taste modifying protein, miraculin, has seven cystein residues in a molecule composed of 191 amino acid residues. Both tetramer miraculin and native dimer miraculin in its crude state have the taste-modifying activity of turning sour tastes into sweet tastes.
Sweetness properties
Miraculin, unlike curculinCurculin
Curculin is a sweet protein that was discovered and isolated in 1990 from the fruit of Curculigo latifolia , a plant from Malaysia. Like miraculin, curculin exhibits taste-modifying activity; however, unlike miraculin, it also exhibits a sweet taste by itself. After consumption of curculin, water...
(another taste-modifying agent), is not sweet by itself, but it can change a sour beverage into a sweet beverage, even for a long period after consumption. The anti-sweet compound, Gymnemic acid
Gymnemic acid
Gymnemic acids are glycosides isolated from the leaves of Gymnema sylvestre . Gymnemic acids like ziziphin and hodulcine are anti-sweet compounds, or sweetness inhibitors. After chewing the leaves, solutions sweetened with sucrose taste like water.More than 20 homologues of gymnemic acid are found...
suppresses the sweet taste of miraculin, like it does for sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
.
The duration and intensity of the taste-modifying phenomena depends on various factors — miraculin concentration, duration of contact of the miraculin with the tongue, and acid concentration. Maximum sweet-induced response has been shown to be equivalent to the sweetness of 17% sucrose solution.
Glycoprotein is sensitive to heat: when heated over 100 °C, miraculin loses its taste-modifying property. Miraculin activity is inactivated at pH below 3 and pH above 12 at room temperature. The sweet modifying effect stays at pH 4 (in acetate buffer), for 6 months at 5 °C.
The detailed mechanism of the taste-inducing behaviour is still unknown. It has been suggested that the miraculin protein can change the structure of taste cells on the tongue. As a result, the sweet receptors are activated by acids, which are sour in general. This effect remains until the taste bud
Taste bud
Taste buds contain the receptors for taste. They are located around the small structures on the upper surface of the tongue, soft palate, upper esophagus and epiglottis, which are called papillae. These structures are involved in detecting the five elements of taste perception: salty, sour,...
s return to normal. The two histidine
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
residues (i.e. His29 and His59) appear to be mainly responsible for the taste-modifiying behavior. One site maintains the attachment of the protein to the membranes while the other (with attached xylose
Xylose
Xylose is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is the precursor to hemicellulose, one of the main constituents of biomass...
or arabinose
Arabinose
Arabinose is an aldopentose – a monosaccharide containing five carbon atoms, and including an aldehyde functional group.For biosynthetic reasons, most saccharides are almost always more abundant in nature as the "D"-form, or structurally analogous to D-glyceraldehyde.For sugars, the D/L...
) activates the sweet receptor membrane in acid solutions.
Further research at the University of Tokyo using a system of cultured cells which allowed the testing of human taste receptors at various pH to uncover the mechanism.
As already known miraculin binds strongly to the sweet taste receptors on our tongues, however it does not activate receptors at neutral pH.
Once acid is introduced, the miraculin protein changes shape in such a way that it turns on the sweet receptors it is bound to, causing an ultra-sweet sensation without affecting other flavours tasted.
Once the acidic food is swallowed, miraculin returns to the inactive shape until the next acidic food comes along. This can continue for about an hour while it is still bound to the taste receptor.
http://news.discovery.com/human/miracle-fruit-berry-everything-taste-sweet-110926.html
As a sweetener
As miraculin is a readily soluble protein and relatively heat stable, it is a potential sweetenerSugar substitute
A sugar substitute is a food additive that duplicates the effect of sugar in taste, usually with less food energy. Some sugar substitutes are natural and some are synthetic. Those that are not natural are, in general, called artificial sweeteners....
in acidic food (e.g. soft drinks). Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese researchers' more or less successful attempts to mass produce it are focused on recombinant technology. While attempts to express it in yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
and tobacco plants have failed, researchers have succeeded in preparing genetically modified E. coli bacteria, lettuce
Lettuce
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...
and tomatoes that express miraculin. The scientists' crops resulted in 40 microgram
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
s of miraculin per gram
Gram
The gram is a metric system unit of mass....
of lettuce leaves, which was considered a large amount. Two grams of lettuce leaves produced roughly the same amount of miraculin as in one miracle fruit berry.
Miraculin was never approved for use as a sweetener by the United States Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
(FDA). In the 1970s the Miralin Company planned on bringing miraculin to market and was founded with investments by Reynolds Metals
Reynolds Metals
Reynolds Group Holdings is an American packaging company with its roots in the Reynolds Metals Company, was the second largest aluminum company in the United States, and the third largest in the world...
, Barclays, and Prudential
Prudential Financial
The Prudential Insurance Company of America , also known as Prudential Financial, Inc., is a Fortune Global 500 and Fortune 500 company whose subsidiaries provide insurance, investment management, and other financial products and services to both retail and institutional customers throughout the...
. Legal advice and contact with the FDA indicated that miraculin would be approved as generally recognized as safe
Generally recognized as safe
Generally recognized as safe is an American Food and Drug Administration designation that a chemical or substance added to food is considered safe by experts, and so is exempted from the usual Federal Food, Drug, and Cosmetic Act food additive tolerance requirements.-History:On January 1, 1958,...
as the berries had been eaten for centuries in Africa with no reports of adverse reactions (substances used in food prior to January 1, 1958, through either scientific procedures or through experience based on common use in food can be designated GRAS). However, on the eve of the product's launch in 1974 the FDA determined that miraculin would be considered a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
and thus require years more testing. At this point the company's investment capital could not sustain them and Miralin folded. Afterward, Miralin requested the FDA documents under the freedom of information act. The documents were nearly completely blacked out, and the rationale for the sudden change in regulation was not revealed.
Miraculin has a novel food status in the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
. However it is approved in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
as a harmless additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
, according to the List of Existing Food Additives published by the Ministry of Health and Welfare (published by JETRO).
Limitations
Miraculin is a non-heat-stable protein, subject to denaturationDenaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
from heating, and thus miracle berries are not taste-bud active when cooked.
While miraculin changes the perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...
of taste, it does not change the food's chemistry, leaving the mouth and stomach vulnerable to the high acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ity of some foods, such as lemon juice
Lemon juice
The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...
, that may cause irritation if eaten in large quantities.