Phenylthiocarbamide (PTC)

Phenylthiocarbamide 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. 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. 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).