2-Carb-39

Continued from 2-Carb-38

Contents

• 2-Carb-39. Polysaccharides
  • 39.1. Names for homopolysaccharides
  • 39.2. Designation of configuration of residues
  • 39.3. Designation of linkage
  • 39.4. Naming of newly discovered polysaccharides
  • 39.5. Uronic acid derivatives.
  • 39.6. Amino sugar derivatives
  • 39.7. Polysaccharides composed of more than one kind of residue
  • 39.8. Substituted residues
  • 39.9. Glycoproteins, proteoglycans and peptidoglycans
• References for this section

Note. This is a modified version of the 1980 recommendations on polysaccharide nomenclature [7].

2-Carb-39.1. Names for homopolysaccharides

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'.

Note. Examples of established usage of the '-an' ending are: xylan for polymers of xylose, mannan for polymers of mannose, and galactan for polymers of galactose. Cellulose and starch are both glucans, as they are composed of glucose residues.

2-Carb-39.2. Designation of configuration of residues

When the configurational series of the monomer residues is known, D- or L- may be included as a prefix to the name.

Examples:

[4)-α-D-Glcp-(13)-α-D-Glcp-(1]_n

A D-glucan (nigeran)

An L-arabinan (more specifically an α-L-arabinan)

2-Carb-39.3. Designation of linkage

When the major linkage in a homopolysaccharide is known, it may be indicated in the name. The linkage designation shows the carbon atoms involved in the glycosidic bonds. When specific sugars are designated, notation for glycosidic linkages should precede the symbols designating the configuration of the sugar; thus, (14)-α-D-glucan.

Examples:

(21)-β-D-Fructofuranan
(inulin has this structure, with a terminal α-D-glucopyranosyl group)

[4)-α-D-Glcp-(1]_n

(14)-α-D-Glucopyranan (amylose)

Note. When the linkage between monosaccharide units is non-glycosidic (as in the phosphate derivative shown below), use of the glycan terminology is inappropriate; other methods of polymer nomenclature should be employed [20].

Poly[(β-D-ribofuranosyl-5-O-yl)(1-deoxy-D-ribitol-1-C,5-O-diyl)(oxidophosphoryl)]

[5)-β-D-Ribf-(11)-D-Rib-ol-5-P-(O]_n

Such structures do not conform to the original strict definition of 'polysaccharide' but are generally classified as polysaccharides in current practice.

2-Carb-39.4. Naming of newly discovered polysaccharides

Names assigned to newly discovered polysaccharides should end in '-an'.

Examples:

[6)-β-D-Glcp-(1]_n

Pustulan (a glucan from the lichen Umbilicaria pustulata)

[3)-β-D-Glcp-(14)-βL-GlcpA-(14)-β-D-Glcp-(14)-α-L-Rhap-(1]_n

Gellan (a bacterial polysaccharide originally designated S-60)

Note. The name ending in '-an' refers to the unsubstituted polysaccharide. Thus xylan occurs in nature in unacetylated and partially acetylated forms. Xylan designates the unacetylated material, and xylan acetate an acetylated derivative.

Well established names such as cellulose, starch, inulin, chitin, amylose and amylopectin are retained. 'Carrageenan' and 'laminaran' are now often used rather than the older names ending in '-in'.

2-Carb-39.5. Uronic acid derivatives

A polysaccharide (glycan) composed entirely of glycuronic acid residues is named by replacing '-ic acid' by '-an'. The generic name for this group of polysaccharides is 'glycuronan'.

Example:

(14)-α-D-galacturonan (pectin component)

Note. The term glycuronan is used instead of 'polyuronide'; the latter term is incorrect.

2-Carb-39.6. Amino sugar derivatives

A polysaccharide composed entirely of amino sugar residues is named by appropriate modification of the systematic amino sugar name.

Example:

[4)-β-D-Glcp NAc(1]_n

(14)-2-acetamido-2-deoxy-β-D-glucan (chitin)

2-Carb-39.7. Polysaccharides composed of more than one kind of residue

A heteropolysaccharide (heteroglycan) is a polymer containing two or more kinds of sugar (glycose) or modified sugar (e.g. aminodeoxyglycose or glycuronic acid) residue. When the polysaccharide has a principal chain ('backbone') composed of only one type of sugar residue, this residue should be cited last (as a 'glycan' term), and the other types of residue cited as 'glyco-' prefixes in alphabetical order. However, when no single type of sugar residue constitutes the principal chain, all sugar residues should be cited alphabetically as 'glyco-' prefixes, and the name should terminate with the suffix '-glycan'.

Examples:

A D-galacto-D-mannan (guaran)

Note. A less branched D-galacto-D-mannan could be shown in the short form as:

Xanthan

2-Carb-39.8. Substituted residues

When substitution occurs in a polysaccharide (glycan), each type of substitutent is cited in the name at an appropriate position (in alphabetical order).

Examples:

(4-O-Methyl-α-D-glucurono)-D-xylan

2,3-Di-O-acetyl-6-O-tritylamylose

[4)-β-D-GlcpA-(13)-β-D-GlcpNAc-(1]_n
(2-Acetamido-2-deoxy-D-gluco)-D-glucuronoglycan
(hyaluronic acid or hyaluronan)

2-Carb-39.9. Glycoproteins, glycopeptides and peptidoglycans

Polymers containing covalently bound monosaccharide and amino-acid residues are termed glycoproteins, glycopeptides or peptidoglycans. It is not possible to give precise distinctions between these terms. In general, glycoproteins are conjugated proteins containing either oligosaccharide groups or polysaccharide groups having a fairly low relative molecular mass. Proteoglycans are proteins linked to polysaccharides of high molecular mass. Peptidoglycans consist of polysaccharide chains covalently linked to peptide chains. The nomenclature of these compounds is discussed in [11].

Synthetically produced or modified carbohydrate-protein conjugates are sometimes referred to as neoglycoproteins. The nomenclature for the carbohydrate-containing substituents in such structures is analogous to sequential oligosaccharide nomenclature (2-Carb-37.2).

Examples:

Poly-[(3,6-Di-O-methyl-β-D-glucopyranosyl)-(14)-(2,3-di-O-methyl-α-L-rhamnopyranosyl)-(12)-(3-O-methyl-α-L-rhamnopyranosyloxy)-(1-O9)-nonanoyl-(1N]-protein
{[β-D-Glcp3,6Me2-(14)-α-L-Rhap2,3Me2-(12)-α-L-Rhap3Me-(1-O9)-nonanoyl-(1N]n-protein}

Poly-[(3,6-Di-O-methyl-β-D-glucopyranosyl)-(14)-(2,3-di-O-methyl-α-L-rhamnopyranosyl)-(12)-(3-O-methyl-α-L-rhamnopyranosyloxy)-(1-O4')-(3-phenylpropanoyl)-(1N^Lys]-protein

7. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), Polysaccharide nomenclature (Recommendations 1980), Eur. J. Biochem., 126, 439-441 (1982); Pure Appl. Chem., 54, 1523-1526 (1982); J. Biol. Chem., 257, 3352-3354 (1982); Arch. Biochem. Biophys., 220, 330-332 (1983); ref. 2, pp. 174-176.

11. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), Nomenclature of glycoproteins, glycopeptides and peptidoglycans, Eur. J. Biochem., 159, 1-6 (1986); Glycoconjugate J., 3, 123-124 (1986); J. Biol. Chem., 262, 13-18 (1987); Pure Appl. Chem., 60, 1389-1394 (1988); Royal Society of Chemistry Specialist Periodical Report, 'Amino Acids and Peptides', vol. 21, p. 329 (1990); ref. 2, pp. 84-89.

20. IUPAC Commission on Macromolecular Nomenclature, Nomenclature of regular single-strand organic polymers (Recommendations 1975), Pure Appl. Chem., 48, 373-385 (1976); 'Compendium of Macromolecular Nomenclature', Blackwell Scientific Publications, Oxford, p.91 (1991).

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