IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN)
World Wide Web version prepared by G. P. Moss
Department of Chemistry, Queen Mary University of London,
Mile End Road, London, E1 4NS, UK
These Rules are as close as possible to the published version prepared for publication by M. Alan Chester (Blood Centre, University Hospital, S-221 85 Lund, Sweden) with an expert panel convened by C. C. Sweeley (USA) and whose members were S. Basu (USA), H. Egge (Germany), G. W. Hart (USA, co-opted), S. Hakomori (USA), T. Hori (Japan: deceased 1994), P. Karlson (Germany), R. Laine (USA), R. Ledeen (USA), B. Macher (USA), L. Svennerholm (Sweden), G. Tettamanti (Italy) and H. Wiegandt (Germany) [see Adv. Carbohydr. Chem. Biochem. 1999, 55, in press; Carbohydr. Res., 1998, 312, 167-175; Eur. J. Biochem., 1998, 257, 293-298; Glycoconjugate J., 1999, 16, 1-6; J. Mol. Biol., 1999, 286, 963-970; Pure Appl. Chem., 1997, 69, 2475-2487; Copyright IUPAC and IUBMB; reproduced with the permission of IUPAC and IUBMB]. If you need to cite these rules please quote these references as their source. In setting up the World Wide Web version some errors were detected and appropriate corrections have been made. The changes have been marked by which is a link to details of the change and where it applies. A PDF of the printed version is available.
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Glycolipids are glycosyl derivatives of lipids such as acylglycerols, ceramides and prenols. They are collectively part of a larger family of substances known as glycoconjugates. The major types of glycoconjugates are glycoproteins, glycopeptides, peptidoglycans, proteoglycans, glycolipids and lipopolysaccharides. The structures of glycolipids are often complex and difficult to reproduce in the text of articles and certainly cannot be referred to in oral discussions without a nomenclature that implies specific chemical structural features.
The 1976 recommendations  on lipid nomenclature contained a section (Lip-3) on glycolipids, with symbols and abbreviations as well as trivial names for some of the most commonly occurring glycolipids. Since then, more than 300 new glycolipids have been isolated and characterized, some having carbohydrate chains with more than twenty monosaccharide residues and others with structural features such as inositol phosphate. The nomenclature needs to be convenient and practical, as well as extensible, to accommodate newly discovered structures. It should also be consistent with the nomenclature of glycoproteins, glycopeptides and peptidoglycans , oligosaccharides , and carbohydrates in general .
This document supersedes the glycolipid section in the 1976 Recommendations on lipid nomenclature .
GL-2. GENERIC TERMS
The term glycolipid designates any compound containing one or more monosaccharide residues bound by a glycosidic linkage to a hydrophobic moiety such as an acylglycerol, a sphingoid, a ceramide (N-acylsphingoid) or a prenyl phosphate.
The term glycoglycerolipid is used to designate glycolipids containing one or more glycerol residues.
The term glycosphingolipid designates lipids containing at least one monosaccharide residue and either a sphingoid or a ceramide. The glycosphingolipids can be subdivided as follows:
A) Neutral glycosphingolipids:
1) mono-, oligo-, and polyglycosylsphingoids
2) mono-, oligo-, and polyglycosylceramides.
B) Acidic glycosphingolipids:
1) sialoglycosphingolipids (gangliosides, containing one or more sialic acid residues)
2) uronoglycosphingolipids (containing one or more uronic acid residues)
3) sulfoglycosphingolipids (containing one or more carbohydrate-sulfate ester groups)
4) phosphoglycosphingolipids (containing one or more phosphate mono- or diester groups)
5) phosphonoglycosphingolipids (containing one or more (2-aminoethyl)hydroxyphosphoryl groups)
The term glycophosphatidyl inositol is used to designate glycolipids which contain saccharides glycosidically linked to the inositol moiety of phosphatidylinositols (e.g. diacyl-sn-glycero-3-phosphoinositol), inclusive of lyso- (Lip-2.6 in ) species and those with various O-acyl-, O-alkyl-, O-alk-1-en-1-yl- (e.g. plasmanylinositols; ) or other substitutions on their glycerol or inositol residues.
Psychosine was coined historically to designate a monoglycosylsphingoid (i.e. not acylated). The use of this term is not encouraged (Lip-3.4 in ).
GL-2.6. Other names
Other terms such as fucoglycosphingolipid, mannoglycosphingolipid, xyloglycosphingolipid, etc., may be used when it is important to highlight a certain structural feature of the glycolipid.
GL-3. PRINCIPLES OF NOMENCLATURE
GL-3.1. Number of monosaccharide residues
The number of monosaccharide residues in an oligosaccharide is indicated by suffixes such as "diosyl", "triaosyl,", "tetraosyl" etc. [1, 6]. Thus, the general name for the oligosaccharide residue of all glycosphingolipids containing ten monosaccharide residues is "glycodecaosyl"; it might be a glycodecaosylceramide or a 3-glycodecaosyl-1,2-diacyl-sn-glycerol. Recommendations have been made for the nomenclature of oligosaccharides [3, 4].
Note 1: "diosyl" not "biosyl" is the correct suffix.
Note 2: The "a" in "tetraosyl", etc, is not elided in order to differentiate a tetrasaccharide residue (tetraosyl) from a four carbon sugar (tetrose), etc. The "a" in "triaosyl" is added for a similar reason.
GL-3.2. Naming of monosaccharide residues
Monosaccharide residues are named and abbreviated (Table 1) according to the proposed rules of nomenclature recommendations for carbohydrates  (see also the nomenclature of glycoproteins ). The D and L configurational symbols are generally omitted; all monosaccharides are D with the exception of fucose and rhamnose which are L unless otherwise specified.
Recommended abbreviations for some monosaccharides, derivatives and related compounds
|N-acetylneuraminic acid1||Neu5Ac or NeuAc|
|N-glycoloylneuraminic acid1||Neu5Gc or NeuGc|
1 Acylated neuraminic acids and other derivatives of neuraminic acid may also be called sialic acids (abbreviated Sia) when the nature of the N-acyl substituent(s) is not relevant, or is unknown .
2 myo-Inositol with the numbering of the 1D configuration .
GL-3.3. Use of symbols for defining oligosaccharide structures
Using the condensed system of carbohydrate nomenclature [Ref. 2, section 3.7: Ref. 4, 2-Carb-38.5], positions of glycosidic linkages and anomeric configurations are expressed in parentheses between the monosaccharide residues that are thus linked. This principle should be adhered to in full names as well as the abbreviated structures. A "short form" for representing sequences more briefly can be used for specifying large structures. Positions of glycosidic linkages are still given, but the number of the anomeric carbon is omitted, since this is invariable for each monosaccharide, i.e. C-1 for Glc, etc.; C-2 for Neu5Ac, etc.
α-D-Galp-(13)-α-D-Galp- (extended form)
or Gal(α1-3)Gal(α- (condensed form)
or Galα3Galα- or Galα-3Galα- (short form).
GL-3.4. Ring size and conformation
Ring size and conformation should be designated only when firmly established from NMR or other experimental data. Previously published recommendations on the specification of conformation should be consulted [9, 10].
Subsequently, examples will usually be in the more traditional form with parentheses and both anomeric locants, as for example Gal(β1-4)Glc-, but it is understood that the short form (i.e. Galβ4Glc-) is also acceptable.
GL-4. CLASSIFICATION OF GLYCOLIPIDS BASED ON THEIR LIPID MOIETIES
Esters, ethers and glucose derivatives of glycerol are designated by a prefix, denoting the substituent, preceded by a locant. As previously discussed in detail , the carbon atoms of glycerol are numbered stereospecifically, with carbon atom 1 at the top of the formula shown below. To differentiate this numbering system from others that have been used, the glycerol is always accompanied by the prefix sn (for stereospecifically numbered, Lip-1.13 in ) in systematic and abbreviated names.
4.2.1. Glycophosphatidyl inositol (GPI) nomenclature should incorporate the accepted IUB-IUPAC recommendations [1, 2] for the naming of phospholipids and the glycan portions of glycolipids or glycoproteins. While the diversity of glycophosphatidylinositol structures is only beginning to be realized (for reviews see [11, 12]), many appear to have a common "core".
4.2.2. Glycophosphatidyl inositols covalently attached to polypeptides are termed "GPI-anchors". Generally, such anchors are covalently attached to the C-terminus of a polypeptide via an amide linkage to an 2-aminoethanol, which is linked to the terminal core mannose residue via a phosphodiester bond on O-6 of the mannose. A core Manα2Manα6Manα4GlcNα6 glycan structure is attached to the inositol (generally D-myo-inositol) of phosphatidylinositol. The non-acetylated GlcN is a characteric feature of glycophosphatidylinositols. Anchor structures appear to vary considerably both in terms of modifications on the core glycan and with respect to additional modifications of the inositol residue. Free glycophosphatidylinositols have generically been termed "glycoinositolphospholipids" to distinguish them from those covalently attached to proteins or larger glycan structures.
4.3.1. A glycosphingolipid is a carbohydrate-containing derivative of a sphingoid or ceramide. It is understood that the carbohydrate residue is attached by a glycosidic linkage to O-1 of the sphingoid.
4.3.2. Sphingoids are long-chain aliphatic amino alcohols. The basic chemical structure is represented by the compound originally called "dihydrosphingosine" [(2S,3R)-2-aminooctadecane-1,3-diol]). This sphingoid should now be referred to  as sphinganine (I).
The terms sphinganine, sphing-4-enine etc. imply a chain length of 18 carbon atoms. Chain-length homologs are named by the root chemical name of the parent hydrocarbon. For example, the sphingoid with 20 carbon atoms is icosasphinganine and the sphingoid with 14 carbon atoms is tetradecasphinganine.
Unsaturated derivatives of sphinganine and other sphingoids should be defined in terms of the location and configuration of each olefinic center. The most commonly occurring unsaturated sphingoid was originally called "sphingosine" [(2S,3R,4E)-2-aminooctadec-4-ene-1,3-diol]. It should now be referred to as (4E)-sphing-4-enine or just sphing-4-enine (II). The trivial name "sphingosine" can be retained. As a second example, a C18 sphingoid with two trans double bonds at 4,14 should be called (4E,14E)-sphinga-4,14-dienine.
Substituents such as hydroxyl, oxo, methyl, etc. are referred to by appropriate suffixes that denote the position of each substituent. The sphingoid containing a hydroxyl group at C-4 of sphinganine was originally called "phytosphingosine.". According to the nomenclature adopted in 1976 , it should be called (2S,3S,4R)-2-aminooctadecane-1,3,4-triol. A trivial (but incorrect) name is (R)-4-hydroxysphinganine (III).
4.3.3. Ceramides are N-acylated sphingoids. The fatty acids of naturally occurring ceramides range in chain length from about C16 to about C26 and may contain one or more double bonds and/or hydroxyl substituents at C-2. The complete chemical name for a specific ceramide includes the sphingoid and fatty acyl substituents. For example, a ceramide containing 2-hydroxyoctadecanoic acid and sphing-4-enine should be called (E)-N-(2-hydroxyoctadecanoyl)sphing-4-enine.
GL-5. NEUTRAL GLYCOSPHINGOLIPIDS
The trivial name "cerebroside" was historically used for the substance from brain, β-galactosyl(11)ceramide, and was later modified to include β-glucosyl(11)ceramide from the spleen of a patient with Gaucher's disease. It has become a general term for these two kinds of monoglycosylceramides. However, since other monosaccharides are found in this class, the more structurally explicit terms such as glucosylceramide (GlcCer or better, more explicitly, Glcβ1Cer), galactosylceramide (GalCer), xylosylceramide (XylCer), etc. should be used.
Diosylceramides may be named systematically, e.g. β-D-galactosyl-(14)-β-D-glucosyl-(11)-ceramide. However, it is often more convenient to use the trivial name of the disaccharide and call the structure given above lactosylceramide (LacCer).
GL-5.3. Neutral glycosphingolipids with oligosaccharide chains
5.3.1. Systematic names for glycosphingolipids with larger oligosaccharide chains become rather cumbersome. It is therefore recommended to use semi-systematic names in which trivial names for "root" structures are used as a prefix. The recommended root names and structures are given in Table 2.
The name of a given glycosphingolipid is then composed of (root name)(root size)osylceramide. Thus, lactotetraosylceramide designates the second structure listed in Table 2 linked to a ceramide. When referring to particular glycose residues Roman numerals are used (Lip-3.9 in ), counting from the ceramide (see Table 2).
TABLE 2. Root names and structures
IV III II I
1 Lacto as used here should not be confused with lactose (Lac).
2 Note: The prefix "iso" is used here to denote a (13) vs. (14) difference in the linkage position between the monosaccharide residues III and II, while the term "neo" denotes such a difference [(14) vs. (13)] between residues IV and III. This scheme should be used also in other cases where such positional isomers occur, and only in such cases.
The use of the prefix "nor" for unbranched oligosaccharide chains should be abandoned since this prefix has a well-defined meaning ("one carbon atom less") in organic chemistry nomenclature.
5.3.2. The root name applies also to structures that are shorter than the root given in Table 2. Thus, gangliotriaosylceramide is the name for the structure GalNAcβ4Galβ4GlcCer, where the fourth, terminal residue is missing. The trisaccharides obtained from the lacto and neolacto series are identical and in this case the former (shorter) name should be used.
5.3.3. In the lacto series, the residues III and IV can form a repeating unit. Thus, names like neolactohexaosylceramide (not recommended) have been used, even though the chemical nature of the two glycose residues at the non-reducing end are not explicit in the name.
The correct name is β-(N-acetyllactosaminyl)-(13)-neolactotetraosylceramide, where N-acetyllactosaminyl is β-D-Galp-(14)-D-GlcNAc-
5.3.4. Substances containing glycose residues that are not part of a root structure should be named by referral to the root oligosaccharide and locating the additional substituents by a Roman numeral designating the position of the substituent in the root oligosaccharide (counting from the ceramide end) to which the substituent is attached, with an arabic numeral superscript indicating the position on that residue which is substituted. The anomeric configuration should also be specified.
5.3.5. Branched structures should be designated in a systematic manner, locating substituents in correlation with the Haworth structure of the multiply substituted monosaccharide. This principle should be applied in full structures as well as linear formulations, wherein substituents are in one or more sets of square brackets. Such names and abbreviations should refer to the substituent on the highest carbon number of the branched monosaccharide first, and proceed toward the substituent on the lowest carbon number. This recommendation is consistent with the nomenclature of glycoproteins, glycopeptides and peptidoglycans  although not explicitly stated therein.
Note: When root names (see GL-5.3.1) are used, the branches should be treated as side chains and named accordingly even when linked to a carbon atom with a higher number than the member of the root oligosaccharide. In oligosaccharide nomenclature  the longest chain is the parent structure. If two chains are of equal length the one with lower locants at the branch points is preferred, although some oligosaccharides are traditionally depicted otherwise - frequently NeuAc and Fuc derivatives.
or GalNAcβ4(Neu5Acα3)Galβ4Glc-. Otherwise in : Neu5Acα3(GalNAcβ4)Galβ4Glc-
GL-6. ACIDIC GLYCOSPHINGOLIPIDS
Gangliosides are sialoglycosphingolipids. They are named as N-acetyl- or N-glycoloylneuraminosyl derivatives of the corresponding neutral glycosphingolipid, using the nomenclature given in GL-5.3. The position of the sialic acid residue(s) is indicated in the same way as is the case of a branched structure.
Gangliosides containing neuraminic acid residues (with O-acyl or other substituents) should be named accordingly, with the positions of the substituents given.
These are best named according to the guidelines of GL-5.2 and GL-5.3. Special root names have not yet been assigned.
These are glycosphingolipids carrying a sulfate ester group, formerly called "sulfatides.". They are sometimes termed sulfatoglycosphingolipids.
Sulfoglycosphingolipids may also be named as sulfate esters (sulfates) of the neutral glycosphingolipids (see GL-5).
or lactosylceramide II3-sulfate.
Two types of glycosphingolipids containing phosphodiester bonds are known: (i) those containing a 2-aminoethyl phosphate residue esterified to a monosaccharide residue, and (ii) those with a phosphodiester bridge between an inositol residue and the ceramide moiety.
Those of the first type can be easily named by analogy to the sulfoglycosphingolipids.
The second type can be named as inositolphosphoceramide derivatives
These are glycolipids esterified with an alkylphosphono acid, i.e. a compound containing a C-P bond. Their nomenclature is best derived using the prefix phosphoryl that denotes the trivalent radical O=P. The residue
may be termed (2-aminoethyl)hydroxyphosphoryl. The location of this group is given in the same way as other ester groups.
GL-7. SHORT ABBREVIATIONS
There are no easy solutions to the dilemma that has arisen from the discovery of so many (nearly 300) glycosphingolipids of diverse structures. Short abbreviations are so attractive that a logical system, with broad application to more complex compounds, is desirable.
GL-7.1. Recommended abbreviations
A system already used (GL-5.3) is based on the abbreviated root names of the oligosaccharide structures. The full root structures are tetrasaccharides, and sequential removal of terminal monosaccharide residues gives smaller, precisely defined structures. Elongation of root tetrasaccharides is on the other hand undefined and hence ambiguous. The root name may be used, followed by an arabic number indicating the total number of monosaccharide residues. A lower case letter can be added to differentiate between particular compounds.
Either of these compounds could, after definition, be referred to as Gb5Cer. In the presence of both structures the abbreviations Gb5a and Gb5b may be defined and used. It is recommended that the use of "Ose", as in GbOse4Cer, be discontinued.
Since this short form sometimes leads to ambiguities, the full structure should be given once in a paper or in a footnote, using the abbreviated form according to GL-5.3.
GL-7.2. The Svennerholm abbreviations for brain gangliosides
In this system, the fact that we are dealing with gangliosides is indicated by the letter G, the number of sialic acid residues is stated by M for mono-, D for di-, T for tri- and Q for tetrasialoglycosphingolipids. A number is then assigned to the individual compound which referred initially to its migration order in a certain chromatographic system .
Though these designations are far from being systematic, and it is impossible to derive the structure from them, they have the advantage of being short and well understood since they have been in use for a long time. A list of these abbreviations is given in Table 3.
Since there is no clear-cut system in these abbreviations, it is not recommended to extend the list by coining new symbols of this kind. As a result, the following two cases are examples of abbreviations that should not be used.
1) A disialoganglioside, Neu5Acα3Galβ3(Neu5Acα6)GalNAcβ4Galβ4GlcCer has been abbreviated GD1α. This practice should be discontinued. The recommended abbreviation for this compound is IV3-α-Neu5Ac,III6-α-Neu5Ac-Gg4Cer.
2) The system has been extended to gangliosides of other "root" types, such as those derived from lactotetraosylceramide. An example of this kind is the widely distributed ganglioside called sialoparagloboside, Neu5Acα3Galβ4GlcNAcβ3Galβ4GlcCer, which has at times been abbreviated LM1, but should be referred to as IV3-α-Neu5Ac-nLc4Cer.
TABLE 3. Some abbreviations using the Svennerholm system
* Previously written using subscripts, e.g. GM3, etc.
Attempts to abbreviate more complex glycosphingolipids derived from these examples have resulted in other illogical abbreviations, such as Fuc-3'-LM1 for Neu5Acα3Galβ4-(Fucα3)GlcNAcβ3Galβ4GlcCer (IV3-α-Neu5Ac,III3-α-Fuc-nLc4Cer).
More information on the structures of various glycolipids and the biological material from which they were obtained may be found in several reviews [14-16].
1 IUPAC-IUB Commission on Biochemical Nomenclature (CBN). The nomenclature of lipids (Recommendations 1976). Eur. J. Biochem. 79, 11-21 (1977); Hoppe-Seylers Z. Physiol. Chem. 358, 617-631 (1977); Lipids 12, 455-468 (1977); Mol. Cell. Biochem. 17, 157-171 (1977); Chem. Phys. Lipids 21, 159-173 (1978); J. Lipid Res. 19, 114-128 (1978); Biochem. J. 171, 21-35 (1978).
2 IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). Nomenclature of glycoproteins, glycopeptides and peptidoglycans (Recommendations 1985). Eur. J. Biochem. 159, 1-6 (1986); Glycoconjugate J. 3,, 123-134 (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).
3 IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). Abbreviated terminology of oligosaccharide chains (Recommendations 1980). Eur. J. Biochem. 126, 433-437 (1982); J. Biol. Chem. 257, 3347-3351 (1982); Pure Appl. Chem. 54, 1517-1522 (1982); Arch. Biochem. Biophys. 220, 325-329 (1983).
4 IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN). Nomenclature of carbohydrates (Recommendations 1996). Pure Appl. Chem. 68, 1919-2008 (1996); Carbohydr. Res. 297, 1-90 (1997); J. Carbohydr. Chem. 16, 1191-1280 (1997); Adv. Carbohydr. Chem. Biochem. 52, 43-177 (1997).
5 W. L. Roberts, S. Santikarn, V. N. Reinhold, and T. L. Rosenberry, J. Biol. Chem. 263, 18776-18784 (1988).
6 C. C. Sweeley. and B. Siddiqui, in The Glycoconjugates, Vol. 1, (M. I. Horowitz and W. Pigman, eds.), pp. 459-540. Academic Press, New York, pp. 459-540 (1977).
7 G. Reuter and, R. Schauer, Glycoconjugate J. 5, 133-135 (1988).
8 Nomenclature Committee of IUB (NC-IUB). Numbering of atoms in myo-inositol (Recommendations 1988). Biochem. J. 258, 1-2 (1989); Eur. J. Biochem. 180, 485-486 (1989).
9 IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). Conformational nomenclature for five- and six-membered ring forms of monosaccharides and their derivatives (Recommendations 1980). Eur. J. Biochem. 111, 295-298 (1980); Arch. Biochem. Biophys. 207, 469-472 (1981); Pure Appl. Chem. 53, 1901-1905 (1981).
10 IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). Symbols for specifying the conformation of polysaccharide chains (Recommendations 1981). Eur. J. Biochem. 131, 5-7 (1983); Pure Appl. Chem. 55, 1269-1272 (1983).
11 M. G. Low and A. R. Saltiel, Science 239, 268-275 (1988).
12 M. A. J. Ferguson and A. F. Williams, Annu. Rev. Biochem. 57, 285-320 (1988).
13 L. Svennerholm, J. Neurochem. 10, 612-623 (1963).
14 H. Wiegandt, in Glycolipids, (A. Neuberger and L. L. M.A., van Deenen L. L. M., eds.), New Comprehensive Biochemistry, Vol 10, p. 28, Elsevier, New York, (1985).
15 S. Hakomori, in Handbook of Lipid Research Vol. 3, (J. N. Kanfer and S. Hakomori, eds.), Vol. 3, pp 1-165. Plenum Press, New York and London (1983) pp 1-165.
16 C. L. M. Stults, C. C. Sweeley and B. A. Macher, Methods Enzymol. 179, 167-214 (1989); see also B. A. Macher and C. C. Sweeley, Methods Enzymol. 50, 236 (1978).