pyrimidine (redirected from Pyrimidine nucleosides)

pyrimidine (pīrĭm`ĭdēn'), type of organic base found in certain coenzymes and in the nucleic acids of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosine, thymine, and uracil.

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pyrimidine

Any of a class of heterocyclic compounds with a ring structure of four carbon and two nitrogen atoms. The simplest member, pyrimidine itself (C₄H₄N₂), is not common, but derivatives with the structure are. Examples include thiamine (vitamin B₁), several sulfa drugs, barbiturates, and three of the bases in nucleic acids (cytosine, thymine, and uracil).

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pyrimidine [pə′rim·ə‚dēn]

(biochemistry)

C₄H₄N₂A heterocyclic organic compound containing nitrogen atoms at positions 1 and 3; naturally occurring derivatives are components of nucleic acids and coenzymes.

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Pyrimidine

A heterocyclic organic

(2)

compound ( 1 ) containing nitrogen atoms at positions 1 and 3. Naturally occurring derivatives of the parent compound are of considerable biological importance as components of nucleic acids and coenzymes and, in addition, synthetic members of this group have found use as pharmaceuticals. See Coenzyme, Nucleic acid

Pyrimidine compounds which are found universally in living organisms include uracil ( 2 ), cytosine ( 3 ), and thymine

(3)

( 4 ). Together with purines these substances make up the “bases” of nucleic acids, uracil and cytosine being found characteristically in ribonucleic acids, with thymine replacing uracil in deoxyribonucleic acids. A number of related pyrimidines also occur in lesser amounts in certain nucleic acids. Other pyrimidines of general natural occurrence are orotic acid and thiamine (vitamin B₁). See Deoxyribonucleic acid (DNA), Purine, Ribonucleic acid (RNA)

Among the sulfa drugs, the pyrimidine derivatives, sulfadi-azine, sulfamerazine, and sulfamethazine, have general formula ( 5 ).

(4)

These agents are inhibitors of folic acid biosynthesis in microorganisms. The barbiturates are pyrimidine derivatives which possess potent depressant action on the central nervous system.