Pyrimidine

One of the two classes of bases in DNA and RNA. The pyrimidine bases are thymine (T) and cytosine (C) in DNA and thymine (T) and uracil (U) in RNA.

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1,3-Diazine; a heterocyclic substance, the formal parent of several “bases” present in nucleic acid s (uracil, thymine, cytosine) as well as of the barbiturates.

- p. 5′-nucleotidase an enzyme that catalyzes the hydrolysis of a p.-nucleoside 5′-monophosphate to produce orthophosphate and the p. nucleoside; a deficiency of this enzyme results in accumulation of p. nucleotides leading to hemolytic anemia.

- p. transferase SYN: thiamin pyridinylase.

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py·rim·i·dine pī-'rim-ə-.dēn, pə- n

1) a weakly basic organic compound C₄H₂N₂ of penetrating odor that is composed of a single six-membered ring having four carbon atoms with nitrogen atoms in positions one and three

2) a derivative of pyrimidine having its characteristic ring structure esp a base (as cytosine, thymine, or uracil) that is a constituent of DNA or RNA

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n.

a nitrogen-containing compound with a ring molecular structure. The commonest pyrimidines are cytosine, thymine, and uracil, which form the nucleotide of nucleic acids.

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py·rim·i·dine (pə-rimґĭ-dēn) an organic compound, a metadiazine, C₄H₄N₂, which is the fundamental form of the pyrimidine bases. These are mostly oxy or amino derivatives, for example, 2,4-dioxypyrimidine is uracil, 2-oxy-4-aminopyrimidine is cytosine, and 2,4-dioxy-5-methylpyrimidine is thymine, all of which are constituents of nucleic acid. See illustration of purine and pyrimidine bases, under base.