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A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups. In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or the N1 of a ...
Glycosidic bonds of the form discussed above are known as O-glycosidic bonds, in reference to the glycosidic oxygen that links the glycoside to the aglycone or reducing end sugar. In analogy, one also considers S-glycosidic bonds (which form thioglycosides ), where the oxygen of the glycosidic bond is replaced with a sulfur atom.
(a) Three hydrogen bonding edges of the four nucleotides (Guanine), showing nomenclature of each edge and (b) Cis and Trans orientations of the sugar moieties of the two nucleotide residues glycosidic bonds of a base pair with respect to hydrogen bonding direction. The arrows in (b) indicate glycosidic bonds as vectors.
Cytosine, thymine, and uracil are pyrimidines, hence the glycosidic bonds form between their 1 nitrogen and the 1' -OH of the deoxyribose. For both the purine and pyrimidine bases, the phosphate group forms a bond with the deoxyribose sugar through an ester bond between one of its negatively charged oxygen groups and the 5' -OH of the sugar. [2]
Schematic showing the structure of nucleoside triphosphates. Nucleosides consist of a 5-carbon sugar (pentose) connected to a nitrogenous base through a 1' glycosidic bond. Nucleotides are nucleosides with a variable number of phosphate groups connected to the 5' carbon. Nucleoside triphosphates are a specific type of nucleotide.
Because most heterocyclic bases contain multiple nucleophilic sites, site selectivity is an important issue in nucleoside synthesis. Purine bases, for instance, react kinetically at N 3 and thermodynamically at N 1 (see Eq. (4)). [4] Glycosylation of thymine with protected 1-acetoxy ribose produced 60% of the N 1 nucleoside and 23% of the N 3 ...
Most glycosyltransferase enzymes form one of two folds: GT-A or GT-B. Glycosyltransferases (GTFs, Gtfs) are enzymes that establish natural glycosidic linkages.They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur ...
Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose (ribofuranose) ring via a β-N 9-glycosidic bond.Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate (cGMP), guanosine diphosphate (GDP), and guanosine triphosphate (GTP).