Glycosylation components

Cycloserine (Fig- 4) is produced by several species of Streptomyces. One of the basic glycosyl components of the bacterial cell wall, n-acetyl-muramic acid (the product of Mur A and MurB), is modified by the addition of the first three amino acids sequentially by MurC, MurD and MurE enzymes. A dipeptide, D-alanyl-D-alanine is then added to make the pentapeptide. In bacteria, L-alanine is the native form and it is converted to D-alanine form by alanine racemase (Air). Two D-alanines are joined by D-ala-D-ala ligase (DdlA) to synthesize the dipeptide. Cycloserine resembles the substrate for Air and Ddl and inhibits their respective reactions in stage I of the peptidoglycan biosynthesis (Fig. 2). 

Two unusual glycosyl esters of cytidine 5 -pyrophosphate were found in extracts of Azotobacter vinelandii,62 The branched-chain, O-methylated heptose called vinelose was identified as the glycosyl component, and the structures 13 and 14 were assigned to these... 

Forsberg, L.S., Carlson, R.W. Structural characterization of the primary O-antigenic polysaccharide of the Rhizobium leguminosarum 3841 lipopolysaccharide and Identification of a new 3-acetimidoylamino-3-deoxyhexuronic acid glycosyl component A unique O-methylated gly-can of uniform size containing 6-deoxy-3-0-methyl-D-talose, N-acetylquinovosamine, and rhizoaminuronic acid (3-acetimidoylamino-3-deoxy-D-g/ co-hexuronic acid). J Biol Chem 283 (2008) 16037-16050. 

A new glycosylated component is related to apoptosis of tumor cells, which is found in E. fetida by Xie et al. [81] recently, and is highly homologous to EFEs and some serine proteases, such as F-I-l, -1-2, -II,... 

EXAMPLE 3.12 The structures of two different disaccharides, both composed of glucose, are shown in Fig. 3-14. The numbering indicates which carbon atoms are linked via the glycosidic bond and whether the bond is a or P with respect to the first residue (the glycosyl component). 

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