Question

Model 1 The oligosaccharide component from a Ceramide (a sphingolipid, see Figure 10-12, page 371 in the textbook) has been removed by treatment with an endoglycosidase. The oligosaccharide is then exhaustively methylated and subject to acid hydrolysis whereby the following monosaccharides are obtained: 2,3,4-trimethyl-L-fucose Asmehu D.SINAC 4,6-dimethyl-D-galactose 2,4,6-trimethyl-D-galactose 2,3,4,6-tetramethyl-D-galactose 2,3,6-trimethyl-D-glucose Next the intact oligosaccharide is subjected to a series of exoglycosidases in the following order. (Each time assume the remaining oligosaccharide is then treated with the next exeglycosidase.) Step 1: c-Fucosidass yields an L-fucose molecule and the remainder of the oligosaccharide (i.e. pentasaccharide). Step 2: a-Galactosidase yields one galactose molecule and the remainder of the oligosaccharide (i.e. tetrasaccharide). Step 3: B-Galactosidase yields a galactose molecule and the remainder of the oligosaccharide (i.e. trisaccharide). Step 4: B-N-Aestylglucosaminidase yields a molecule of GINAs and a dissacsbaride. Step 5: the disaccharide is then hydrolyzed into two monosaccharides using B-Galactosidase. Draw the complete structure of this oligosaccharide and show it as it would appear attached to the core ceramide. Explain your reasoning. (i.e. don't just draw the final structure, let me see your logie in deriving it.) Determine the blood type of this glycosphingolipid (figure 10-14, page 372, and use the additional information sheet).

Answer 1

Solution:

Squential acid hydrolysis of a oligo saccharide called ceramide-hexasaccharide with exoglycosidase gives the following 6 mono saccharides.

Step 1: Hexasaccharide-Cer + $\alpha$ -Fucosidase $\rightarrow$ L-Fucose + Pentasaccharide-Cer

Step 2: Pentasaccharide-Cer + $\alpha$ -Galactosidase $\rightarrow$ D-Galactose + tetrasaccharide-Cer

Step 3: tetrasaccharide-Cer + $\beta$ -Galactosidase $\rightarrow$ D-Galactose + trisaccharide-Cer

Step 4: trisaccharide-Cer + $\beta$ -N-Acetylglucosaminidase $\rightarrow$ D-GlcNAc + disaccharide-Cer

Step 5: disaccharide-Cer  + $\beta$ -Galactosidase $\rightarrow$ D-Glucose + D-Galactose + Cer

Based on the above squential acid hydrolysis one can write the Hexasaccharide-Cer structure as follows

B GINAC-(143)-Gal(1463) Gal-(2-44)-Gel- (144) Glen –(+1) Cer (i) fuc

Blood type determination:

The structural rigidity of the A or B blood group type maintained and determined by Fucosyl residue at 2-position of penaltimate glucose residue and is immunospecific to A type blood group.