Pyrimidine
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| Pyrimidine | |
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| Chemical name | Pyrimidine |
| Chemical formula | C4H4N2 |
| Molecular mass | 80.09 g/mol |
| Density | 1.016 g/ml |
| Melting point | 20 - 22 °C |
| Boiling point | 123 - 124 °C |
| CAS number | 289-95-2 |
| SMILES | C1=NC=NC=C1 |
| Missing image Pyrimidine_chemical_structure.png Chemical structure of pyrimidine | |
Pyrimidine is a heterocyclic aromatic organic compound, which is similar to benzene and pyridine and that contains two nitrogen atoms at positions 1 and 3 of the six-membered ring.
Three nucleobases found in nucleic acids, namely cytosine, thymine, and uracil, are pyrimidine derivatives. In DNA and RNA, these bases form hydrogen bonds with their complementary purines.
purine pyrimidine A T G C
In RNA, the complement of A is U instead of T:
purine pyrimidine A U G C
| Missing image Thymine_chemical_structure.png Chemical structure of thymine | Missing image Uracil_chemical_structure.png Chemical structure of uracil | Missing image Cytosine_chemical_structure.png Chemical structure of cytosine |
| Thymine | Uracil | Cytosine |
These hydrogen bonding modes are for classical Watson-Crick base pairing. Other hydrogen bonding modes are available in both DNA and RNA, although the additional 2'-hydroxyl group of RNA expands the configurations through which RNA can form hydrogen bonds.
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Pyrimidine biosynthesis
Pyrimidine de novo biosynthesis
Unlike purines, pyrimidines are assembled before being attached to 5-phosphoribosyl-1-pyrophosphate (PRPP). The first step begins with formation of carbamoyl phosphate by carbamoyl phosphate synthetase II. The second major step is the creation carbamoyl aspartic acid formed by aspartic transcarbamolyase. Once orotic acid is eventually formed from carbamoyl aspartic acid, it is combined with PRPP to form uridine-3'-phosphate (UMP). UMP is then phosphorylated twice to form ribose-PPP-Uridine-5'-triphosphate (UTP).
Cytidino-5'-triphosphate (CTP) is formed from UTP utilizing glutamine.
Pyrmidine catabolism
Pyrimidines are broken down completely to CO2. H2O and urea. Cytosine can be broken down to uracil which can be further broken down to N-carbaomyl-β-alanine. Thymine is broken down into β-aminoisobutyrate which can be further broken down into intermediates eventually leading into the citric acid cycle. β-aminoisobutyrate acts as a rough indicator for rate of DNA turnover.
Suppliers/Manufacturers
- Lancaster (http://www.lancastersynthesis.com/homecatsearch.htm) (now part of Alfa)
- Fisher (https://www1.fishersci.com/index.jsp)
- VWR (http://www.vwr.com/index.htm)
- Alfa (http://www.alfa.com/alf/index.htm)
- Aldrich (http://www.sigmaaldrich.com)
- Aurora Fine Chemicals (http://www.aurora-feinchemie.com)
See also
- Pyrazine, an analog with the nitrogen atoms in positions 1 and 4.
- Simple aromatic rings
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