Thiouracil

**Semantic type:** Nucleic Acid, Nucleoside, or Nucleotide|Organic Chemical|Pharmacologic Substance

**Definition:** A sulfur-containing uracil. An established antithyroid drug and highly selective inhibitor of nitric oxide synthase (NOS), thiouracil also covalently binds to dopaquinone, produced by tyrosinase catalyzed oxidation of tyrosine, thereby selectively accumulating in de novo-synthesized melanin in overactive melanin-producing cells and providing a means to localize melanoma cells. (NCI04)

**Synonyms:** - THIOURACIL