Hexose, protein-bound

A mixture of lentil lectin-reactive glycoproteins from pig lymphocyte-plasma membrane was isolated by lentil lectin-Sepharose chromatography of sodium deoxycholate-solubilized membranes.445 Eighty-seven percent of the protein applied (17% of hexose) passed through unretarded, and 13% of the applied protein (83% of hexose) was bound, and eluted with methyl a-D-glucopyranoside solution. Recovery was 95% of the material applied, in contrast to the recovery in similar experiments conducted on con A-Sepharose columns (80% recovery).850 The eluate from the lentil column, which contained at least ten glycoproteins, blocked lymphocyte transformation induced by lentil or kidney-bean lectins.445... 

The interaction of polysilicic acids with polysaccharides appears to be an open field for investigation. There may be some common factor, as further evidenced by the finding that in the serum of silicotic patients there is an increase in mucoproteins and protein-bound hexoses, along with higher level of silica (248). Some association of polysaccharides with silica has probably existed since life began because in a primitive organism such as the diatom, when silica is deficient the cells become coated with a polyuronide of glucuronic residues (42), and no doubt the microporous silica skeleton is interpenetrated by this polymer. 

It appears to be reasonably certain, however, that part of the hexose associated with collagen is firmly bound to the protein and probably takes part in the cross-linking of the polypeptide chains. The role of the hexoses in collagen will be distaissed further in Section VII. 

In the natural state, the chains are often joined by glycosidic bonds to an L-serine residue of a polypeptide backbone. Other types of linkage also occur, as in keratan sulfate.84 It is not yet known whether hyaluronic acid is bound covalently to protein. The main part of each chain approximates to a regular alternation of residues of 2-acetamido-2-deoxy-D-hexose and of another sugar (often a uronic acid), but the sequence near the L-serine residues is different. In chondroitin 4-sulfate,85 it is ... 

Glycosylated haemoglobins have been isolated following ion-exchange chromatography of haemolysed erythrocytes. Bound hexoses, after release from the protein by hydrolysis with oxalic acid, were measured as 5-hydroxy-... 

The RBP molecule is a single polypeptide chain of about 180-185 amino acid residues containing three intramolecular disulfide bonds (as cystine residues) (Rask et al., 1981). No fatty acid or fatty acyl chains were detected in purified RBP (Kanai et al., 1968). Analyses for carbohydrate showed that RBP was free of neutral sugar and hexosamine (Peterson, 1971) and had a maximum of 0.9 mol of hexose per mol of protein (Raz et al., 1970). It is likely that RBP contains no bound lipid (other than retinol) and no carbohydrate. 

For both hexoses and pentoses, the mono-, di-, and oligosaccharides and their derivatives are taken up via specific membrane-bound transport proteins. Few detailed studies of sugar uptake by the clostridia have been reported, but observations made to date indicate that the transport mechanisms are similar to those found in a wide variety of other bacteria (Mitchell 1998). A large number of genes for different types of transporters have been found in the genome of C. acetobutylicum ATCC 824 (Nblling et al. 2001). 

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