N1glycosidic

N1 glycosidic, referring to an N1 glycosidic bond, is a type of N-glycosidic linkage in nucleosides that connects the anomeric carbon (C1') of the sugar (ribose or deoxyribose) to the N1 atom of a pyrimidine base. In nucleosides of RNA and DNA, this bond forms between the sugar and pyrimidine bases such as cytosine, uracil, or thymine. The linkage is typically a beta-glycosidic bond, reflecting the stereochemistry of the sugar.

This type of bond is contrasted with the N9 glycosidic bond used by purine bases (adenine and guanine), where the sugar is attached at the N9 position. Therefore, N1 glycosidic bonds are characteristic of pyrimidine nucleosides, including cytidine (cytosine linked to ribose), uridine (uracil linked to ribose), and thymidine or deoxythymidine (thymine linked to deoxyribose).

Chemical and biological significance: the N1 glycosidic bond is essential for forming natural nucleosides that constitute RNA and DNA building blocks. It can be hydrolyzed under acidic conditions or by specific enzymes, releasing the free base and the sugar. In cellular metabolism, nucleoside formation involves glycosylation of the corresponding base with activated sugar, while nucleoside turnover and repair systems may remove or modify these bonds as part of nucleotide salvage pathways and base-excision processes.

In summary, N1 glycosidic bonds are the pyrimidine-specific N-glycosidic linkages connecting the C1' of ribose or deoxyribose to the N1 position of pyrimidine bases, forming cytidine, uridine, and thymidine nucleosides.