Phenylthiocarbamide

Phenylthiocarbamide, also known as PTC, or phenylthiourea, is an organic compound having the unusual property of either tasting very bitter, or being 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. There is conflicting evidence whether a higher percentage of women taste PTC versus men.

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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 (PTC, 6-n-propylthiouracil) and dietary habits. 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 four SNP's (single nucleotide polymorphisms) along the gene that may render the proteins made from it, tasteless. There is conflicting evidence whether this trait of tasting is caused by dominance or incomplete dominance. Any person with a single copy of the taster gene can taste. Some studies have shown though, that homozygous tasters taste a more intense bitterness that people who are heterozygous. Other studies have pointed that there may be another gene that determines how well the person tastes on another chromosome.

See also

• TAS2R38
• List of Mendelian traits in humans

References

• Fischer, R., Griffin, F. and Kaplan, A. R.. "Taste Thresholds, Cigarette Smoking, and Food Dislikes". Medicina experimentalis. International journal of experimental medicine 9: 151-67. PMID 14083335.

• Kaplan, A. R., Glanville, E. V. and Fischer, R. (1964). "Taste Thresholds for Bitterness and Cigarette Smoking". Nature 202: 1366. PMID 14210998.

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