Cytosine is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached. The nucleoside of cytosine is cytidine. In Watson–Crick base pairing, it forms three hydrogen bonds with guanine.
Pyrimidine is an aromatic, heterocyclic, organic compound similar to pyridine. One of the three diazines, it has nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine and pyridazine.
Uracil is one of the four nucleobases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine.
Thymine is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. In RNA, thymine is replaced by the nucleobase uracil. Thymine was first isolated in 1893 by Albrecht Kossel and Albert Neumann from calf thymus glands, hence its name.
Nucleobases are nitrogen-containing biological compounds that form nucleosides, which, in turn, are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Five nucleobases—adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical. They function as the fundamental units of the genetic code, with the bases A, G, C, and T being found in DNA while A, G, C, and U are found in RNA. Thymine and uracil are distinguished by merely the presence or absence of a methyl group on the fifth carbon (C5) of these heterocyclic six-membered rings. In addition, some viruses have aminoadenine (Z) instead of adenine. It differs in having an extra amine group, creating a more stable bond to thymine.
In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. Ribonucleotides themselves are basic monomeric building blocks for RNA. Deoxyribonucleotides, formed by reducing ribonucleotides with the enzyme ribonucleotide reductase (RNR), are essential building blocks for DNA. There are several differences between DNA deoxyribonucleotides and RNA ribonucleotides. Successive nucleotides are linked together via phosphodiester bonds.
DNA glycosylases are a family of enzymes involved in base excision repair, classified under EC number EC 3.2.2. Base excision repair is the mechanism by which damaged bases in DNA are removed and replaced. DNA glycosylases catalyze the first step of this process. They remove the damaged nitrogenous base while leaving the sugar-phosphate backbone intact, creating an apurinic/apyrimidinic site, commonly referred to as an AP site. This is accomplished by flipping the damaged base out of the double helix followed by cleavage of the N-glycosidic bond.
Uramustine (INN) or uracil mustard is a chemotherapy drug which belongs to the class of alkylating agents. It is used in lymphatic malignancies such as non-Hodgkin's lymphoma. It works by damaging DNA, primarily in cancer cells that preferentially take up the uracil due to their need to make nucleic acids during their rapid cycles of cell division. The DNA damage leads to apoptosis of the affected cells. Bone marrow suppression and nausea are the main side effects.
Dihydropyrimidine dehydrogenase deficiency is an autosomal recessive metabolic disorder in which there is absent or significantly decreased activity of dihydropyrimidine dehydrogenase, an enzyme involved in the metabolism of uracil and thymine.
In enzymology, a dihydrouracil dehydrogenase (NAD+) (EC 1.3.1.1) is an enzyme that catalyzes the chemical reaction
In enzymology, a dihydrouracil oxidase (EC 1.3.3.7) is an enzyme that catalyzes the chemical reaction
In enzymology, a dihydropyrimidinase (EC 3.5.2.2) is an enzyme that catalyzes the chemical reaction
Uracil-DNA glycosylase is an enzyme. Its most important function is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosidic bond and initiating the base-excision repair (BER) pathway.
Single-strand selective monofunctional uracil DNA glycosylase is an enzyme that in humans is encoded by the SMUG1 gene. SMUG1 is a glycosylase that removes uracil from single- and double-stranded DNA in nuclear chromatin, thus contributing to base excision repair.
Dihydropyrimidinase is an enzyme that in humans is encoded by the DPYS gene.
Tegafur is a chemotherapeutic prodrug of 5-fluorouracil (5-FU) used in the treatment of cancers. It is a component of the combination drug tegafur/uracil. When metabolised, it becomes 5-FU.
The molecular formula C4H6N2O2 may refer to:
Interchim is a privately owned French company specialized in manufacturing and distribution of reagents, consumables and dedicated instruments for the R&D and industry laboratory in the fields of fine chemistry, chromatography and bio-analysis. It has become a provider of reference methods, products for analytics serving research and quality control in the biomedical field, pharmaceutical industry, but also cosmetics and environment.
Somatic hypermutation is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it. A major component of the process of affinity maturation, SHM diversifies B cell receptors used to recognize foreign elements (antigens) and allows the immune system to adapt its response to new threats during the lifetime of an organism. Somatic hypermutation involves a programmed process of mutation affecting the variable regions of immunoglobulin genes. Unlike germline mutation, SHM affects only an organism's individual immune cells, and the mutations are not transmitted to the organism's offspring. Because this mechanism is merely selective and not precisely targeted, somatic hypermutation has been strongly implicated in the development of B-cell lymphomas and many other cancers.
7,8-didemethyl-8-hydroxy-5-deazariboflavin synthase (EC 4.3.1.32, FO synthase) and 5-amino-6-(D-ribitylamino)uracil—L-tyrosine 4-hydroxyphenyl transferase (EC 2.5.1.147) are two enzymes always complexed together to achieve synthesis of FO, a precursor to Coenzyme F420. Their systematic names are 5-amino-5-(4-hydroxybenzyl)-6-(D-ribitylimino)-5,6-dihydrouracil ammonia-lyase (7,8-didemethyl-8-hydroxy-5-deazariboflavin-forming) and 5-amino-6-(D-ribitylamino)uracil:L-tyrosine, 4-hydroxyphenyl transferase respectively. The enzymes catalyse the following chemical reactions:
