Phenylthiocarbamide

Last updated
Phenylthiocarbamide
Phenylthiocarbamide structure.svg
Phenylthiourea-from-xtal-3D-balls.png
Names
Preferred IUPAC name
Phenylthiourea
Other names
N-Phenylthiourea
1-Phenylthiourea
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.002.865 OOjs UI icon edit-ltr-progressive.svg
MeSH Phenylthiourea
PubChem CID
UNII
  • InChI=1S/C7H8N2S/c8-7(10)9-6-4-2-1-3-5-6/h1-5H,(H3,8,9,10) X mark.svgN
    Key: FULZLIGZKMKICU-UHFFFAOYSA-N X mark.svgN
  • InChI=1/C7H8N2S/c8-7(10)9-6-4-2-1-3-5-6/h1-5H,(H3,8,9,10)
    Key: FULZLIGZKMKICU-UHFFFAOYAW
  • C1=CC=C(C=C1)NC(=S)N
Properties
C7H8N2S
Molar mass 152.22 g·mol−1
AppearanceWhite to slightly yellow powder
Density 1.294 g/cm3
Melting point 145 to 150 °C (293 to 302 °F; 418 to 423 K)
Soluble in boiling water
Hazards
GHS labelling: [1]
GHS-pictogram-skull.svg
Danger
H300, H317
P280, P301+P310+P330, P302+P352
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
1
0
Lethal dose or concentration (LD, LC):
3 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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

Contents

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 often treated as a dominant genetic trait, although inheritance and expression of this trait are somewhat more complex. [2] [3]

PTC also inhibits melanogenesis and is used to grow transparent fish. [4]

About 70% of people can taste PTC, varying from a low of 58% for Indigenous Australians and indigenous peoples of New Guinea to 98% for indigenous peoples of the Americas. [5] 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. [6] [7] PTC does not occur in food, but related chemicals do, and food choice can be related to a person's ability to taste PTC. [6] [8]

History

The tested genetic taste phenomenon of PTC was discovered in 1931 when DuPont chemist Arthur Fox [lower-alpha 1] accidentally released a cloud of 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 penetrance was so strong that it was used in paternity tests before the advent of DNA matching. [9]

The PTC taste test has been widely used in school and college practical teaching as an example of Mendelian polymorphism in human populations. Based on a taste test, usually of a piece of paper soaked in PTC (or the less toxic propylthiouracil (PROP)), students are divided into taster and non-taster groups. By assuming that PTC tasting is determined by a dominant allele at a single autosomal gene, and that the class is an unbiased sample from a population in Hardy–Weinberg equilibrium, students then estimate allele and genotype frequencies within the larger population. While this interpretation is broadly consistent with numerous studies of this trait, it is worth noting that other genes, sex, age and environmental factors influence sensitivity to PTC. [2] [3] Also, there are several alleles segregating at the major gene determining the taste of PTC, particularly in African populations, and the common "taster" allele is incompletely dominant (homozygotes for this allele are more sensitive to PTC than are heterozygotes). [3] [10] Additionally, PTC is toxic and sensitivity to the substitute, PROP, does not show a strong association with the gene controlling ability to taste PTC. [3]

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. [5] 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).

In 1976, an inverse relationship between taster status for PTC and for a bitter component of the fruit of the tree Antidesma bunius was discovered. [11] Research on the implications still continues.

Ability to taste PTC may be correlated with a dislike of plants in the genus Brassica , presumably due to chemical similarities. However, studies in Africa show a poor correlation between PTC tasting and dietary differences. [10]

Genetics

Much of the variation in tasting of PTC is associated with polymorphism at the TAS2R38 taste receptor gene. [12] In humans, there are three SNPs (single nucleotide polymorphisms) along the gene that may render its proteins unresponsive. [13] There is conflicting evidence as to whether the inheritance of this trait is dominant or incompletely dominant. [3] 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. [2]

The frequency of PTC taster and non-taster alleles vary in different human populations. [14] The widespread occurrence of non-taster alleles at intermediate frequencies, much more common than recessive alleles conferring genetic disease, across many isolated populations, suggests that this polymorphism may have been maintained through balancing selection. [10]

Chimpanzees and orangutans also vary in their ability to taste PTC, with the proportions of tasters and non-tasters similar to that in humans. [15] The ability to taste PTC is an ancestral trait of hominids that has been independently lost in humans and chimpanzees, through distinct mutations at TAS2R38. [16]

Non-taster phenotype distribution in selected populations

Results of multiple PTC taste tests in different regions done with the discrimination method developed by Harris and Kalmus in 1949, published in Annals of Eugenics . [17]
Location# of ParticipantsNon-taster %References
Bosnia and Herzegovina 7,36232.02Hadžiselimović et al. (1982) [18]
Croatia 20027.5Grünwald, Pfeifer (1962)
Czech Republic 78532.7Kubičkova, Dvořaková (1968)
Denmark 25132.7Harrison et al. (1977) [19]
England 44131.5Harrison et al. (1977) [19]
Hungary 43632.2Forai, Bankovi (1967)
Italy 1,03129.19Floris et al. (1976)
Montenegro 25628.20Hadžiselimović et al. (1982) [18]
Užice, Serbia 1,12916.65Hadžiselimović et al. (1982) [18]
Voivodina, Serbia 60026.3Božić, Gavrilović (1973)
Russia 48636.6Boyd (1950)
Slovenia 12637.3Brodar (1970)
Spain 20425.6Harrison et al. (1977) [19]

Notes

  1. ↑ Arthur L. Fox commented in his 1932 paper: "Some time ago the author had occasion to prepare a quantity of phenyl thio carbamide, and while placing it in a bottle the dust flew around in the air. Another occupant of the laboratory, Dr. C. R. Noller, complained of the bitter taste of the dust, but the author, who was much closer, observed no taste and so stated. He even tasted some of the crystals and assured Dr. Noller they were tasteless but Dr. Noller was equally certain it was the dust he tasted. He tried some of the crystals and found them extremely bitter. With these two diverse observations as a starting point, a large number of people were investigated and it was established that this peculiarity was not connected with age, race or sex. Men, women, elderly persons, children, negroes, Chinese, Germans and Italians were all shown to have in their ranks both tasters and non-tasters." [lower-alpha 2]
    Fox's finding received immediate attention, appearing in brief news stories in both Science and The Scientific News Letter. These stories focused on the curiosity of the finding, but they also caught the attention of geneticists, who were beginning to explore the organization of the human genome. Botanist Albert Francis Blakeslee replicated Fox's basic results and reported that PTC taste-blindness appears to be a recessive gene. [lower-alpha 3]
  2. Fox, Arthur L. (January 1932). "The Relationship between Chemical Constitution and Taste". Proceedings of the National Academy of Sciences. 18 (1): 115–120. doi:10.1073/pnas.18.1.115. ISSN   0027-8424.
  3. Wooding, Stephen (April 2006). "Phenylthiocarbamide: A 75-Year Adventure in Genetics and Natural Selection". Genetics. National Center for Biotechnology Information, United States National Library of Medicine . Retrieved August 4, 2024.

See also

Related Research Articles

An allele, or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule.

<span class="mw-page-title-main">Dominance (genetics)</span> One gene variant masking the effect of another in the other copy of the gene

In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second is called recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes (autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child. Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance, such as incomplete dominance, in which a gene variant has a partial effect compared to when it is present on both chromosomes, and co-dominance, in which different variants on each chromosome both show their associated traits.

A genetic screen or mutagenesis screen is an experimental technique used to identify and select individuals who possess a phenotype of interest in a mutagenized population. Hence a genetic screen is a type of phenotypic screen. Genetic screens can provide important information on gene function as well as the molecular events that underlie a biological process or pathway. While genome projects have identified an extensive inventory of genes in many different organisms, genetic screens can provide valuable insight as to how those genes function.

<span class="mw-page-title-main">Human variability</span> Range of possible values for any characteristic of human beings

Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.

Ecological genetics is the study of genetics in natural populations. It combines ecology, evolution, and genetics to understand the processes behind adaptation.

<span class="mw-page-title-main">Single-nucleotide polymorphism</span> Single nucleotide in genomic DNA at which different sequence alternatives exist

In genetics and bioinformatics, a single-nucleotide polymorphism is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently large fraction of the population, many publications do not apply such a frequency threshold.

<i>Brassica oleracea</i> Species of plant

Brassica oleracea is a plant species from family Brassicaceae that includes many common cultivars used as vegetables, such as cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy cabbage, kohlrabi, and gai lan.

Supertasters are people whose sense of taste for certain flavors and foods is far more sensitive than the average person. The term originated with experimental psychologist Linda Bartoshuk and is not the result of response bias or a scaling artifact but appears to have an anatomical or biological basis.

Genetic association is when one or more genotypes within a population co-occur with a phenotypic trait more often than would be expected by chance occurrence.

<span class="mw-page-title-main">TAS2R16</span> Protein-coding gene in the species Homo sapiens

TAS2R16 is a bitter taste receptor and one of the 25 TAS2Rs. TAS2Rs are receptors that belong to the G-protein-coupled receptors (GPCRs) family. These receptors detect various bitter substances found in nature as agonists, and get stimulated. TAS2R16 receptor is mainly expressed within taste buds present on the surface of the tongue and palate epithelium. TAS2R16 is activated by bitter β-glucopyranosides

<span class="mw-page-title-main">Cruciferous vegetables</span> Vegetables of the family Brassicaceae

Cruciferous vegetables are vegetables of the family Brassicaceae with many genera, species, and cultivars being raised for food production such as cauliflower, cabbage, kale, garden cress, bok choy, broccoli, Brussels sprouts, mustard plant and similar green leaf vegetables. The family takes its alternative name from the shape of their flowers, whose four petals resemble a cross.

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A phene is an individual genetically determined characteristic or trait which can be possessed by an organism, such as eye colour, height, behavior, tooth shape or any other observable characteristic.

<span class="mw-page-title-main">TAS2R38</span> Protein-coding gene in the species Homo sapiens

Taste receptor 2 member 38 is a protein that in humans is encoded by the TAS2R38 gene. TAS2R38 is a bitter taste receptor; varying genotypes of TAS2R38 influence the ability to taste both 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC). Though it has often been proposed that varying taste receptor genotypes could influence tasting ability, TAS2R38 is one of the few taste receptors shown to have this function.

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The evolution of bitter taste receptors has been one of the most dynamic evolutionary adaptations to arise in multiple species. This phenomenon has been widely studied in the field of evolutionary biology because of its role in the identification of toxins often found on the leaves of inedible plants. A palate more sensitive to these bitter tastes would, theoretically, have an advantage over members of the population less sensitive to these poisonous substances because they would be much less likely to ingest toxic plants. Bitter-taste genes have been found in a host of vertebrates, including sharks and rays, and the same genes have been well characterized in several common laboratory animals such as primates and mice, as well as in humans. The primary gene responsible for encoding this ability in humans is the TAS2R gene family which contains 25 functional loci as well as 11 pseudogenes. The development of this gene has been well characterized, with proof that the ability evolved before the human migration out of Africa. The gene continues to evolve in the present day.

A taster is a person, by means of a human genotype, who is able to taste phenylthiocarbamide (PTC) and its derivative 6-n-propylthiouracil (PROP). PTC tastes bitter to many people (tasters) but is tasteless to others (non-tasters).

<span class="mw-page-title-main">PTC tasting</span>

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Dennis T. Drayna is an American human geneticist known for his contributions to stuttering, human haemochromatosis, pitch, and taste. He is currently the Section Chief of Genetics of Communication Disorders at the U.S. National Institute for Deafness and Other Communication Disorders.

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References

  1. ↑ GHS: Record of Phenylthiourea in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 2021-12-22.
  2. 1 2 3 Guo; Reed, D. R. (2001). "The genetics of phenylthiocarbamide perception". Annals of Human Biology. 28 (2): 111–142. doi:10.1080/03014460151056310. PMC   3349222 . PMID   11293722.
  3. 1 2 3 4 5 McDonald, John H. "PTC tasting: The Myth". Myths of Human Genetics. Retrieved 11 May 2015.
  4. ↑ 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. S2CID   7980753.
  5. 1 2 Kim U, Wooding S, Ricci D, Jorde LB, Drayna D (2005). "Worldwide haplotype diversity and coding sequence variation at human bitter taste receptor loci". Human Mutation. 26 (3): 199–204. doi: 10.1002/humu.20203 . PMID   16086309. S2CID   31248094.
  6. 1 2 Fischer R, Griffin F, Kaplan AR (1963). "Taste thresholds, cigarette smoking, and food dislikes". Medicina Experimentalis. International Journal of Experimental Medicine. 9 (3): 151–67. doi:10.1159/000135346. PMID   14083335.
  7. ↑ Kaplan AR, Glanville EV, Fischer R (1964). "Taste thresholds for bitterness and cigarette smoking". Nature. 202 (4939): 1366. Bibcode:1964Natur.202.1366K. doi: 10.1038/2021366a0 . PMID   14210998. S2CID   4184237.
  8. ↑ Forrai G, Bánkövi G; Bánkövi (1984). "Taste perception for phenylthiourea and food choice—a Hungarian twin study". Acta Physiol Hung. 64 (1): 33–40. PMID   6541419.
  9. ↑ Lee Phillips M (15 July 2003). "Scientists Find Bitter Taste Gene" . Retrieved 5 December 2009.
  10. 1 2 3 Campbell; et al. (2012). "Evolution of Functionally Diverse Alleles Associated with PTC Bitter Taste Sensitivity in Africa". Molecular Biology and Evolution. 29 (4): 1141–1153. doi:10.1093/molbev/msr293. PMC   3341826 . PMID   22130969.
  11. ↑ Henkin, R.I. & W.T. Gillis (1977). "Divergent taste responsiveness to fruit of the tree Antidesma bunius". Nature. 265 (5594): 536–537. Bibcode:1977Natur.265..536H. doi:10.1038/265536a0. PMID   834304. S2CID   1259447.
  12. ↑ Drayna, Dennis (2005). "Human Taste Genetics". Annual Review of Genomics and Human Genetics. 6: 217–235. doi: 10.1146/annurev.genom.6.080604.162340 . PMID   16124860.
  13. ↑ 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. Bibcode:2003Sci...299.1221K. doi:10.1126/science.1080190. PMID   12595690. S2CID   30553230.
  14. ↑ 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): 161–166. doi: 10.1016/j.ejmhg.2012.01.003 .
  15. ↑ Fisher, Ford & Huxley, R. A.; Ford, E. B.; Huxley, Julian (28 October 1939). "Taste-testing the Anthropoid Apes" (PDF). Nature. 144 (750): 750. Bibcode:1939Natur.144..750F. doi: 10.1038/144750a0 . hdl:2440/15129. S2CID   4136526.
  16. ↑ Wooding, Stephen; et al. (2006). "Independent evolution of bitter-taste sensitivity in humans and chimpanzees". Nature. 440 (7086): 930–934. Bibcode:2006Natur.440..930W. doi:10.1038/nature04655. PMID   16612383. S2CID   4395892.
  17. ↑ Harris, H.; Kalmus, H. (1949). "The measurement of taste sensitivity to phenylthiourea (PTC)". Annals of Eugenics. 15 (1): 24–31. doi: 10.1111/j.1469-1809.1949.tb02419.x . PMID   15403125.
  18. 1 2 3 Hadžiselimović, R.; Novosel, V.; Bukvić, S.; Vrbić, N. (1982). "Distribucija praga nadražaja za ukus feniltiokarbamida (PTC) u tri uzorka stanovništva Jugoslavije". God. Biol. Inst. Univ. U Sarajevu. 35: 72–80.
  19. 1 2 3 Harrison et al. (1977): Human biology – An introduction to human evolution, variation, growth and ecology. Oxford University Press, Oxford, ISBN   978-0-19-857164-3; ISBN   978-0-19-857165-0.
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