Monosaccharide residues

Antibiotic A201A. Antibiotic A201A (23), produced by S. capreolus is an /V -dimethyladenine nucleoside stmcturaHy similar to puromycin (19). Compound (23) which contains an aromatic acid and monosaccharide residues (1,4), inhibits the incorporation of amino acids into proteins but has no effect on RNA or DNA synthesis. Compound (23) does not accept polypeptides as does (19), and does appear to block formation of the initiation complex of the SOS subunit. It may block formation of a puromycin-reactive ribosome. 

Carb-29. Hemiacetals and hemithioacetals 2-Carb-30. Acetals, ketals and their thio analogues 2-Carb-31. Names for monosaccharide residues... 

Oligosaccharide and polysaccharide structures occur not only in free form but often as parts of glycopeptides or glycoproteins [11] or of glycolipids [21]. It can be cumbersome to designate their structures by using the recommendations of 2-Carb-37. The use of three-letter symbols for monosaccharide residues is therefore recommended. With appropriate locants and anomeric descriptors, long sequences can thus be adequately described in abbreviated form. 

Symbols for the common monosaccharide residues and derivatives are listed in Table 2. They are generally derived from the corresponding trivial names. Abbreviations for substituents (see 2-Carb-1.16.2), preceded by locants, follow the monosaccharide abbreviations directly. 

Table 2. Symbols for monosaccharide residues and derivatives in oligosaccharide chains...

A general term for a polysaccharide (glycan) composed of a single type of monosaccharide residue is obtained by replacing the ending -ose of the sugar name by -an . 

Glycosides are formed by condensation between the hydroxyl group of the anomeric carbon of a monosaccharide, or monosaccharide residue, and a second compound that may—or may not (in the case of an aglycone)—be another monosaccharide. If the second group is a hydroxyl, the O-glycosidic bond is an acetal link because it results from a reaction between a hemiacetal group (formed from an aldehyde and an —OH group) and an-... 

Carbohydrates are major constiments of animal food and animal tissues. They are characterized by the type and number of monosaccharide residues in their molecules. 

The monosaccharide residues identified in fractions 6-12 are 1-linked GalA... 

TABLE A.5. The Masses of Some Monosaccharide Residues and Their Derivatives... 

Monosaccharide residues containing vicinal hydroxyl groups are oxidized by periodate, and are subsequently removed in the reduction-hydrolysis step. Therefore, the positions to which such monosaccharide residues are linked can be located by methylation analysis performed before, and after, Smith degradation. Alternatively,59 the oxidized and reduced sample is methylated, the ether hydrolyzed, and the product realkylated with CD3I or CH3CH2I. This kind of procedure can have advantages over that first described. For example, methylation before the hydrolysis step hinders the acetal protection of hydroxyl groups that can occur in acid hydrolysis.7... 

Figure 9.17 Alpha and beta anomers of maltose. When only the hydroxyl group on the anomeric carbon of one of the monosaccharide residues is involved in the glyco-sidic linkage, the anomeric hydroxyl group on the other residue is still free. This permits two possible orientations, which are described as either alpha or beta forms of the monosaccharide residue.

Relative orientations of pendant groups with respect to the monosaccharide residues. 

Because carbohydrates are so frequently used as substrates in kinetic studies of enzymes and metabolic pathways, we refer the reader to the following topics in Ro-byt s excellent account of chemical reactions used to modify carbohydrates formation of carbohydrate esters, pp. 77-81 sulfonic acid esters, pp. 81-83 ethers [methyl, p. 83 trityl, pp. 83-84 benzyl, pp. 84-85 trialkyl silyl, p. 85] acetals and ketals, pp. 85-92 modifications at C-1 [reduction of aldehydes and ketones, pp. 92-93 reduction of thioacetals, p. 93 oxidation, pp. 93-94 chain elongation, pp. 94-98 chain length reduction, pp. 98-99 substitution at the reducing carbon atom, pp. 99-103 formation of gycosides, pp. 103-105 formation of glycosidic linkages between monosaccharide residues, 105-108] modifications at C-2, pp. 108-113 modifications at C-3, pp. 113-120 modifications at C-4, pp. 121-124 modifications at C-5, pp. 125-128 modifications at C-6 in hexopy-ranoses, pp. 128-134. 

In addition to the esters of uridine 5 -pyrophosphate with monosaccharide sulfates, hen oviduct contains corresponding esters with two saccharides. The first known member of this series was a unique derivative 41, in which the monosaccharide residues are linked... 

Analysis of LLO from controls reveals predominantly an LLO structure consisting of 14 monosaccharide residues (Glc3Man9GlcNAc2), whereas CDG-patients with defined type-I deficiencies show shortened LLO profiles, which help to identify defects in patients with unknown CDG-I types. 

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