Globosides

Globosides are a group of chemical compounds called glycosphingolipids with neutral oligosaccharides as head groups. The sugar units are hexoses. The first sugar unit is glycosidically linked to the C1-OH group of a ceramide .

Differentiation from other glycosphingolipids

Differentiation from cerebrosides

The globosides can be distinguished from the cerebrosides within the group of glycosphingolipids in that they have more than one hexose on the ceramide. The cerebrosides have only one monosaccharide as a head group. In the case of globosides, however, a further hexose is linked to the first sugar unit of the ceramide (i.e. the hexose bound to the C1-OH group of the ceramide). The following sugars are always bound to the previous, last sugar. Sulphatides are galactocerebrosides (cerebrosides with galactose as sugar) with a sulphate residue on the C3 atom of the galactose residue. However, the fact that the globosides have oligosaccharides as head groups is not sufficient for the final differentiation within the glycosphingolipids. The gangliosides also have an oligosaccharide as a head group.

Differentiation from gangliosides

Globosides are to be distinguished from gangliosides in that they do not contain any N-acetylneuraminic acid (NANA) . In gangliosides, at least one N-acetylneuraminic acid is always bound to a galactose residue. This first galcatose residue is usually in the second position in the saccharide chain. At the same time, another sugar unit is bound to this second sugar unit. With the gangliosides, two further molecules can be bound to a previous sugar unit. Another NANA can be bound to the first NANA molecule. In addition, other NANA molecules can be bound to other galactose residues.

N-acetylneuraminic acid must not be confused with N-acetylgalactosamine , which occurs as hexose in both gangliosides and globosides.

N-acetylgalactosamine is a derivative of galactosamine (an amino sugar of galactose), which in turn is a derivative of galcatose . It is therefore the N-acetylated form of an amino sugar (galactosamine) of galactose .

N-acetylneuraminic acid, on the other hand, is a derivative of neuraminic acid (an amino sugar of mannose), which in turn is a derivative of mannosamine (amino sugar), which in turn is a derivative of mannose. It is therefore the N-acetylated form of an amino sugar (neuraminic acid) of mannose .

Connection with diseases

The globoside blood group P antigen is localized on the erythrocytes . It consists of P ₁ - , P- and P _k - antigens and forms a receptor for the parvovirus B19 . There are four different phenotypes for the globoside:

• P ₁ and P ₂ , which have the globoside and can be infected with it;
• P _1k and P phenotypes do not have the receptor and are therefore resistant to the B19 virus.

Individual evidence

1. ^ Donald Voet / Judith G. Voet: Biochemistry, 2011, John Wiley and Sons, ISBN 978-0470-91745-9 , p. 1008.
2. ↑ Globoside - an overview | ScienceDirect Topics. Retrieved June 10, 2020 . 
3. ↑ Veot and Voet; BIOCHEMISTRY; Second edition; FIGURE 23-73
4. ↑ Helmut Gadner: Pediatric Hematology and Oncology , 2006, Springer-Verlag , ISBN 3-540-03702-0 .
5. ↑ Detlev Ganten: Molecular medicine basics of fetal and neonatal diseases , 2005, Springer-Verlag , ISBN 3-540-20138-6 .