Abstract
Oligosaccharides in human blood are involved in various blood group antigens. Sialo-oligosaccharide-rich glycoproteins (GPs) in red blood cell (RBC) membranes also carry M, N, Ss and other blood group antigens. However, teleost blood is not expressed as a blood group antigen. Our study showed that carp, yellow tail and red sea bream GPs exhibit broad-spectrum antibiotic activity. This bacteriostatic activity is caused by the sialo-oligosaccharides from GPs.
Based on NMR and GC–MS results, the structure of the bacteriostatic sialo-oligosaccharide from carp GP was determined to be NeuGcα2→6(Fucα1→4) (Glcα1→3) Galβ1→4GalNAc-ol. Compared to carp pentose, the structure of human GP O-linked tetra- or tri-oligosaccharides is simpler. In addition, NeuAc is simpler in human GPs than in carp NeuGc.
In contrast to human blood, teleost blood does not contain IgG, and other antibodies occur at low levels. Teleost GPs may act as substitutes for antibodies, such as IgG, in the immune system. In this review, the transformation of the physiological function of oligosaccharides with respect to their structure is described.