pyrimidine


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pyrimidine

(pīrĭm`ĭdēn'), type of organic base found in certain coenzymescoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
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 and in the nucleic acidsnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
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 of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosinecytosine
, organic base of the pyrimidine family. It was isolated from the nucleic acid of calf thymus tissue in 1894. A suggested structure for cytosine, published in 1903, was confirmed in the same year when that base was synthesized in the laboratory.
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, thyminethymine
, organic base of the pyrimidine family. Thymine was the first pyrimidine to be purified from a natural source, having been isolated from calf thymus and beef spleen in 1893–4.
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, and uraciluracil
, organic base of the pyrimidine family. It was isolated from herring sperm and also produced in a laboratory in 1900–1901. When combined with the sugar ribose in a glycosidic linkage, uracil forms a derivative called uridine (a nucleoside), which in turn can be
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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

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(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 ).

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(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.

Pyrimidine

 

(also called 1,3-diazine), a heterocyclic compound. Colorless crystals; melting point, 21°C; boiling point, 124°C. Pyrimidine is readily soluble in water, alcohol, and ether. The structural formula is

Pyrimidine is a very weak, monoacidic base that forms quaternary salts, each of which contains a single nitrogen atom; it also reacts with hydrogen peroxide (H2O2) to yield N-oxides. Pyrimidine does not enter readily into electrophilic substitution reactions, for example, halogenation, sulfonation, and nitration, but the hydrogen atom on the carbon in position number four is easily replaced in reactions with organomagnesium compounds, organolithium compounds, NaNH2, and KOH. Pyrimidine is synthesized by reduction of its 2,4,6-trichloro derivative, which is a product of the reaction of POCI3 with barbituric acid. Pyrimidine and its derivatives are components of individual nucleotides and of nucleic acids, the most important biopolymers. They also occur in many biologically active substances, including thiamine, the antibiotic, amicetin, and barbiturates.

pyrimidine

[pə′rim·ə‚dēn]
(biochemistry)
C4H4N2 A heterocyclic organic compound containing nitrogen atoms at positions 1 and 3; naturally occurring derivatives are components of nucleic acids and coenzymes.
References in periodicals archive ?
The concentrations of C13:0, iso-C15:0, and C17:0 were significantly and positively linked with pyrimidine contents in rumen.
This team, in a second portion of this experiment, measured the production of molecular products of DNA damage (cyclobutane pyrimidine dimers and 8-OH-dG) within cells to evaluate DNA damage and repair.
The most important mechanism in this process is nucleotide excision DNA repair (NER) which is in charge of cyclobutane pyrimidine dimers and (6-4) photoproducts removal.
The nitrogenous bases Purines [adenine (A) and guanine (G)] and Pyrimidines [Cytosine (C), Uracil (U)and Thymine (T)] are essential building blocks of RNA and DNA.
Besides, 5-FU is a pyrimidine analogue that inhibits DNA synthesis and affects rapidly proliferating cells.
The metabolic pathway genes that highly correlated with variable P6 are enriched in pyrimidine metabolism and terpenoid backbone biosynthesis.
UV radiation induces DNA damage, such as single-strand breaks, pyrimidine dimers, and 6-4 PPs, which induce mutations that are characteristic of the promotion, establishment, and development of tumors [46].
LEF can remarkably decrease the aggregation of inflammatory cells at joints2 and effectively control disease progression3 by inhibiting dihydro-lactate dehydrogenase and tyrosine kinase to reduce pyrimidine formation, by decreasing the number of activated T lymphocytes, and by dramatically suppressing the catalytic capacity of neutrophils.
The applications of these pyrimidine derivatives in different fields of science developed our interest in the measurement of their velocities and viscosities and to compute acoustical parameters to understand their interactions with organic solvent at different concentrations.
This observation strongly suggests that humans suffering from XP are probably prone to cancer in organs other than the skin given sufficient exposure to chemical carcinogens--a result to be expected, based on the observation that NER deals with multiple types of base damage in DNA, not just pyrimidine dimers.
In particular, ENT1 and ENT2 represent the major transporters at the plasma membrane and transport both purines and pyrimidines as well as numerous clinically relevant nucleoside analogs (Baldwin et al.