Globosides are a sub-class of the lipid class

glycosphingolipid Glycosphingolipids are a subtype of glycolipids containing the amino alcohol sphingosine. They may be considered as sphingolipids with an attached carbohydrate. Glycosphingolipids are a group of lipids (more specifically, sphingolipids) and are a p ...

with three to nine

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...

molecules as the side chain (or R group) of

ceramide Ceramides are a family of waxy lipid molecules. A ceramide is composed of N-acetylsphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make up ...

. The sugars are usually a combination of ''N''-acetylgalactosamine, D-glucose or D-galactose. One characteristic of globosides is that the "core" sugars consists of Glucose-Galactose-Galactose (Ceramide-βGlc4-1βGal4-1αGal), like in the case of the most basic globosid
Gb3
also known as pk-antigen. Another important characteristic of globosides is that they are neutral at pH 7, because they usually do not contain

neuraminic acid Neuraminic acid (5-amino-3,5-dideoxy-D-''glycero''-D-''galacto''-non-2-ulosonic acid) is an acidic (in particular ulosonic) amino sugar with a backbone formed by nine carbon atoms. Although 9-carbon sugars do not occur naturally, neuraminic ...

, a sugar with an acidic carboxy-group. However, some globosides with the core structure Cer-Glc-Gal-Gal do contain neuraminic acid, e.g. the globo-series glycosphingolipid "SSEA-4-antigen" The side chain can be cleaved by

galactosidases Galactosidases are enzymes (glycoside hydrolases) that catalyze the hydrolysis of galactosides into monosaccharides. Galactosides can be classified as either alpha or beta. If the galactoside is classified as an alpha-galactoside, the enzyme is ca ...

and

glucosidases Glucosidases are the glycoside hydrolase enzymes categorized under the EC number 3.2.1. Function Alpha-glucosidases are enzymes involved in breaking down complex carbohydrates such as starch and glycogen into their monomers. They catalyze the ...

. The deficiency of

α-galactosidase A α-Galactosidase ( EC 3.2.1.22, α-GAL, α-GAL A; systematic name α-D-galactoside galactohydrolase) is a glycoside hydrolase enzyme that catalyses the following reaction: : Hydrolysis of terminal, non-reducing α-D-galactose residues in α-D- ...

causes

Fabry's disease Fabry disease, also known as Anderson–Fabry disease, is a rare genetic disease that can affect many parts of the body, including the kidneys, heart, and skin. Fabry disease is one of a group of conditions known as lysosomal storage diseases. T ...

, an inherited metabolic disease characterized by the accumulation of the globoside

globotriaosylceramide Globotriaosylceramide is a globoside. It is also known as CD77, Gb3, GL3, and ceramide trihexoside. It is one of the few clusters of differentiation that is not a protein. It is formed by the alpha linkage of galactose to lactosylceramide catalyze ...

. Globoside (GB4) has been known as the receptor for

Parvovirus B19 Primate erythroparvovirus 1, generally referred to as B19 virus (B19V), parvovirus B19 or sometimes erythrovirus B19, is the first (and until 2005 the only) known human virus in the family ''Parvoviridae'', genus ''Erythroparvovirus''; it measur ...

, due to observations that B19V binds to the thin-layered

chromatogram In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...

of the

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

. However, the binding on its surface does not match well with the

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

, which raised debates on whether or not GB4 is the cause for productive infection. Additional research using the technique Knockout Cell Line has shown that although GB4 does not have the direct entry

receptor Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...

for B19V, it plays a post-entry role in productive infection.

References

External links

* * Glycolipids Blood antigen systems Transfusion medicine {{biochemistry-stub