Phenylthiocarbamide

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IUPACName=phenylthiourea
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CASNo= 103-85-5
PubChem=676454
SMILES=C1=CC=C(C=C1)NC(=S)N
MeSHName=Phenylthiourea
Section2= Chembox Properties
Formula=C₇H₈N₂S
MolarMass=152.218
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Phenylthiocarbamide, also known as PTC, or phenylthiourea, is an organic compound that either tastes very bitter, or is virtually tasteless, depending on the genetic makeup of the taster. The ability to taste PTC is a dominant genetic trait. The test to determine PTC sensitivity is one of the most common genetic tests on humans.

About 70% of people can taste PTC, varying from a low of 58% for Aboriginal people 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 whether a higher percentage of women taste PTC versus men.

History

The genetic taste phenomenon of PTC was discovered in 1931 when a DuPont 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 gotten 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.

Role in taste

There is a large body of evidence linking the ability to taste thiourea compounds and dietary habits. Much of this work has focused on 6-propyl-2-thiouracil (PROP), a compound related to PTC that has lower toxicity. See supertaster for more information. Likewise, heavy cigarette smokers are more likely to have high PTC and PROP thresholds (i.e. are relatively insensitive), suggesting taste function may play a protective role against smoking.

Genetics

There are three SNP's (single nucleotide polymorphisms) along the gene that may render its proteins unresponsive. There is conflicting evidence as to whether this trait is a result of either dominance or incomplete dominance. 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 who are heterozygous; other studies have indicated that another gene may determine taste sensitivity.

See also

* TAS2R38
* List of Mendelian traits in humans

References

*

*

* L. Kameswaran, S. Gopalakrishnan, M. Sukumar, (1974). "Phenylthiocarbamide and Naringin Taste Threshold in South Indian Medical Students", Ind. J. Pharmac., 6 (3). 134-140.

* G. Forrai, G. Bánkövi, (1984). "Taste perception for phenylthiocarbamide and food choice--a Hungarian twin study.", Acta Physiol Hung., 64 (1). 33-40.

External links

* [http://www.nidcd.nih.gov/research/scientists/draynad.asp Dennis Drayna's home page.] Drayna has done extensive studies of PTC in various populations
* [http://www.iit.edu/~smile/bi9113.html Population Study and Applications Using PTC Paper]
* [http://genetics-education-partnership.mbt.washington.edu/cool/tools/ptcpaper.html Classroom activity description using PTC paper]
* [http://faculty.washington.edu/chudler/bitter.html A report on the discovery of PTC]
* [http://www.science.edu.sg/ssc/detailed.jsp?artid=5985&type=6&root=4&parent=4&cat=40 Information on PTC in the Population and the effects of PTC on humans]
* Thiourea tasting