N-Glycosidic linkages

Neosidomycin (63) and SF-2140 (64) are indole N-glycosides produced by S. hjgroscopicus A.ctinomadura respectively (195,196). A revised stmcture for (63) has appeared (197). Compound (64) contains an a-N-glycoside linkage. Both (63) and (64) show activity against gram-positive bacteria, yeast, fungi, and vimses. 

Hemiacetal hydroxyl groups of carbohydrate molecules also may be coupled to amine-containing molecules to form N-glycosidic linkages, such as those in nucleic acids and oligonucleotides. 

Figure 1.42 The three pyrimidine bases common to nucleic acid construction. Cytosine and thymine are found in DNA, while in RNA, uracil residues replace thymine. The associated sugar groups are bound in N-glycosidic linkages to the N-l nitrogen.

N-glycosidic linkage, lead to considerable variation in the conformations adopted by double-helix structures. 

The N-glycoside linkages of DNA and RNA are stable in mildly alkaline conditions. However, the phosphodiester linkages of DNA and RNA demonstrate markedly different chemical properties in mild alkali. For example, 0.3 M KOH (37°C) rapidly ( 1 hr) catalyzes the cleavage of all phos-... 

Aspartylglycosylaminase is a lysosomal enzyme that catalyzes the hydrolysis of the N-glycosidic linkage between /V-acetylglucosamine and asparaginyl residues of glycoproteins. 

Each nucleoside has two parts, a sugar and a base, joined together by a p N-glycosidic linkage. 

Nucleoside hydrolase has been proposed to participate in purine salvage in the trypanosome Crithidia fasciculata. The enzyme hydrolyses the N-glycosidic linkage of the naturally occurring purine and pyrimidine nucleosides. A geometric model of the transition state for nucleoside hydrolase for the reaction (Horenstein et al., 1991)... 

A [3-N-glycosidic linkage between N-acetylglucosamine and the amide nitrogen of an asparagine residue of the protein (GIcNAc-Asn). Linkage of wide occurrence. 

Structure of the common branched inner domain of oligosaccharides linked in N-glycosidic linkages with asparagine. Man = Mannose T, GIcNAc = N-acetylglucosamine , Asn = Asparagine. [Adapted with permission from N. Sharon and H. Lis, Chem. Eng. News, p. 28 (March 30, 1981) 1981 by the American Chemical Society.]... 

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