Phenylthiocarbamide

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Phenylthiocarbamide
Phenylthiocarbamide structure.svg Phenylthiourea-from-xtal-3D-balls.png
Identifiers
CAS number 103-85-5 YesY
PubChem 676454
UNII 6F82C6Q54C YesY
MeSH Phenylthiourea
ChEBI CHEBI:46261 N
Jmol-3D images Image 1
Properties
Molecular formula C7H8N2S
Molar mass 152.22 g mol−1
Appearance White to slightly yellow powder
Density 1.294 g/cm3
Melting point 150 °C (302 °F; 423 K)
Solubility in water Soluble in boiling water
Hazards
EU classification Very Toxic T+
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
LD50 3 mg/kg (oral, rat)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Phenylthiocarbamide (PTC), also known as phenylthiourea (PTU), is an organosulfur thiourea containing a phenyl ring.

It has the unusual property that it 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, and the test to determine PTC sensitivity is one of the most commonly used[citation needed] genetic tests on humans.

PTC also inhibits melanogenesis and is used to grow transparent fish.[1]

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.[2][dead link] 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.[3][4] PTC does not occur in food, but related chemicals do, and food choice is related to a person's ability to taste PTC.[3][5] There is conflicting evidence as to whether a higher percentage of women than men can taste PTC.[citation needed]

History[edit]

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 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.[6]

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.[7] Research on the implications still continues.

Some chimpanzees share the ability to taste PTC. However, chimpanzee PTC tasting relies on a different enzyme than human tasting, suggesting that the ability evolved independently in both species.[8]

Role in taste[edit]

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.[2] A supertaster has more of an ability to taste PTC. On the other hand, 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.

Genetics[edit]

There are three SNPs (single nucleotide polymorphisms) along the gene that may render its proteins unresponsive.[9] There is conflicting evidence as to whether the inheritance of this trait is dominant or incomplete dominant.[citation needed] Any person with a single functional copy of this gene can make the protein and is sensitive to PTC.[citation needed] 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.[citation needed]

The frequency of PTC taster and non-taster alleles vary in different human populations.[10]

See also[edit]

References[edit]

  1. ^ Karlsson, Johnny; von Hofsten, Jonas; Olsson, Per-Erik (2001). "Generating Transparent Zebrafish: A Refined Method to Improve Detection of Gene Expression During Embryonic Development". Marine Biotechnology 3 (6): 522–527. doi:10.1007/s1012601-0053-4. PMID 14961324. 
  2. ^ a b "Question No. 19866". Singapore: Science Centre Singapore. Retrieved 5 December 2009. 
  3. ^ a b Fischer, R., Griffin, F. and Kaplan, A. R. (1963). "Taste thresholds, cigarette smoking, and food dislikes". Medicina experimentalis. International journal of experimental medicine 9: 151–67. PMID 14083335. 
  4. ^ Kaplan AR, Glanville EV, Fischer R (1964). "Taste thresholds for bitterness and cigarette smoking". Nature 202 (4939): 1366. doi:10.1038/2021366a0. PMID 14210998. 
  5. ^ Forrai G, Bánkövi G (1984). "Taste perception for phenylthiourea and food choice—a Hungarian twin study". Acta Physiol Hung 64 (1): 33–40. PMID 6541419. 
  6. ^ Lee Phillips M (15 July 2003). "Scientists Find Bitter Taste Gene". Retrieved 5 December 2009. 
  7. ^ Henkin, R.I. and W.T. Gillis (1977). "Divergent taste responsiveness to fruit of the tree Antidesma bunius". Nature 265 (5594): 536–537. doi:10.1038/265536a0. PMID 834304. 
  8. ^ Wooding, Stephen; Bufe, Bernd; Grassi, Christina; Howard, Michael T.; Stone, Anne C.; Vazquez, Maribel; Dunn, Diane M.; Meyerhof, Wolfgang et al. (2006). "Independent evolution of bitter-taste sensitivity in humans and chimpanzees". Nature 440 (7086): 930–4. doi:10.1038/nature04655. PMID 16612383. 
  9. ^ Kim UK, Jorgenson E, Coon H, Leppert M, Risch N, Drayna D (2003). "Positional cloning of the human quantitative trait locus underlying taste sensitivity to phenylthiocarbamide". Science 299 (5610): 1221–1225. doi:10.1126/science.1080190. PMID 12595690. 
  10. ^ Fareed, M.; Shah, A.; Hussain, R.; Afzal, M. (2012). "Genetic study of phenylthiocarbamide (PTC) taste perception among six human populations of Jammu and Kashmir (India)". Egypt J Med Hum Genet 13 (2): 161. doi:10.1016/j.ejmhg.2012.01.003. 

External links[edit]