Phenylthiocarbamide
Encyclopedia
Phenylthiocarbamide, also known as PTC, or phenylthiourea,
is an organosulfur thiourea
containing a phenyl ring.
It has the unusual property that it either taste
s very bitter or is virtually tasteless, depending on the genetic
makeup of the taster. The ability to taste PTC is a dominant genetic trait, and the test to determine PTC sensitivity is one of the most commonly used genetic tests on humans.
Phenylthiocarbamide also inhibits melanogenesis and is used to grow transparent fish.
About 70% of people can taste PTC, varying from a low of 58% for indigenous peoples of Australia and New Guinea to 98% for indigenous peoples of the Americas
. One study has found that non-smokers and those not habituated to coffee
or tea
have a statistically higher percentage of tasting PTC than the general population. PTC does not occur in food, but related chemicals do, and food choice is related to a person's ability to taste PTC. There is conflicting evidence as to whether a higher percentage of women than men can taste PTC.
chemist named Arthur Fox accidentally released a cloud of a fine crystalline PTC. A nearby colleague complained about the bitter taste, while Dr. Fox, who was closer and should have received a strong dose, tasted nothing. Fox then continued to test the taste buds of assorted family and friends, setting the groundwork for future genetic studies. The genetic correlation was so strong that it was used in paternity tests before the advent of DNA
matching.
In 1976, a remarkable inverse relationship between taster status for PTC and for a bitter component of the fruit of the tree Antidesma bunius
was discovered. Research on the implications still continues.
and dietary habits. Much of this work has focused on 6-propyl-2-thiouracil (PROP)
, a compound related to PTC that has lower toxicity. A supertaster
has more of an ability to taste PTC. Likewise, heavy cigarette smokers are more likely to have high PTC and PROP thresholds (i.e. are relatively insensitive).
Ability to taste PTC may be correlated with a dislike of plants in the Brassica
genus, presumably due to chemical similarities.
that may render its proteins unresponsive. There is conflicting evidence as to whether the inheritance of this trait is dominant or incomplete dominant. Any person with a single functional copy of this gene can make the protein and is sensitive to PTC. Some studies have shown that homozygous tasters experience a more intense bitterness than people that are heterozygous; other studies have indicated that another gene may determine taste sensitivity.
is an organosulfur thiourea
Thiourea
Thiourea is an organosulfur compound of with the formula SC2 . It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad...
containing a phenyl ring.
It has the unusual property that it either taste
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
s very bitter or is virtually tasteless, depending on the genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
makeup of the taster. The ability to taste PTC is a dominant genetic trait, and the test to determine PTC sensitivity is one of the most commonly used genetic tests on humans.
Phenylthiocarbamide also inhibits melanogenesis and is used to grow transparent fish.
About 70% of people can taste PTC, varying from a low of 58% for indigenous peoples of Australia and New Guinea to 98% for indigenous peoples of the Americas
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
. One study has found that non-smokers and those not habituated to coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...
or tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...
have a statistically higher percentage of tasting PTC than the general population. PTC does not occur in food, but related chemicals do, and food choice is related to a person's ability to taste PTC. There is conflicting evidence as to whether a higher percentage of women than men can taste PTC.
History
The genetic taste phenomenon of PTC was discovered in 1931 when a DuPontDuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...
chemist named Arthur Fox accidentally released a cloud of a fine crystalline PTC. A nearby colleague complained about the bitter taste, while Dr. Fox, who was closer and should have received a strong dose, tasted nothing. Fox then continued to test the taste buds of assorted family and friends, setting the groundwork for future genetic studies. The genetic correlation was so strong that it was used in paternity tests before the advent of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
matching.
In 1976, a remarkable inverse relationship between taster status for PTC and for a bitter component of the fruit of the tree Antidesma bunius
Antidesma bunius
Antidesma bunius is a species of fruit tree in the Phyllanthaceae. It is native to Southeast Asia, the Philippines, and northern Australia. Its common Philippine name and other names include bignay, bugnay or bignai and currant tree. This is a variable plant which may be short and shrubby or tall...
was discovered. Research on the implications still continues.
Role in taste
There is a large body of evidence linking the ability to taste thiourea compoundsThiourea
Thiourea is an organosulfur compound of with the formula SC2 . It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad...
and dietary habits. Much of this work has focused on 6-propyl-2-thiouracil (PROP)
Propylthiouracil
Propylthiouracil or 6-n-Propylthiouracil is a thioamide drug used to treat hyperthyroidism by decreasing the amount of thyroid hormone produced by the thyroid gland...
, a compound related to PTC that has lower toxicity. A supertaster
Supertaster
A supertaster is a person who experiences the sense of taste with far greater intensity than average. Women are more likely to be supertasters, as are individuals of Asian and African descent. The cause of this heightened response is currently unknown, although it is thought to be, at least in...
has more of an ability to taste PTC. Likewise, heavy cigarette smokers are more likely to have high PTC and PROP thresholds (i.e. are relatively insensitive).
Ability to taste PTC may be correlated with a dislike of plants in the Brassica
Brassica
Brassica is a genus of plants in the mustard family . The members of the genus may be collectively known either as cabbages, or as mustards...
genus, presumably due to chemical similarities.
Genetics
There are three SNPs (single nucleotide polymorphisms) along the geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
that may render its proteins unresponsive. There is conflicting evidence as to whether the inheritance of this trait is dominant or incomplete dominant. Any person with a single functional copy of this gene can make the protein and is sensitive to PTC. Some studies have shown that homozygous tasters experience a more intense bitterness than people that are heterozygous; other studies have indicated that another gene may determine taste sensitivity.
External links
- Dennis Drayna's home page. Drayna has done extensive studies of PTC in various populations
- Population Study and Applications Using PTC Paper
- Classroom activity description using PTC paper Thiourea tasting