Blood group substances biosynthesis

Chapters 17 through 21 deal with carbohydrate-enzyme systems. Hehre presents some new ideas on the action of amylases. Kabat presents some new immunochemical studies on the carbohydrate moiety of certain water-soluble blood-group substances and their precursor antigens. Hassid reviews the role of sugar phosphates in the biosynthesis of complex saccharides. Pazur and co-workers present information obtained by isotopic techniques on the nature of enzyme-substrate complexes in the hydrolysis of polysaccharides. Gabriel presents a common mechanism for the production of 6-deoxyhexoses. An intermediate nucleoside-5 -(6-deoxyhexose-4-ulose pyrophosphate) is formed in each of the syntheses. 

Fig. 9. Proposed composite structure showing the relationship of the A, B, H, Le , and Le antigenic determinants of the water-soluble human blood group substances from ovarian cysts. The structure of the side chain in brackets has not been established, but the existence of such a chain is indicated by the mechanism of alkaline borohydride degradation and the oligosaccharides isolated. The carbohydrate chain shown is one of many linked to the serines and threonines of the polypeptide backbone. Chains are not homogeneous and may be of various lengths depending upon genetic composition, incomplete biosynthesis, and unknown factors. From Pereira and Kabat, modified from Lloyd and Kabat cf. Kabat. ...

Figure 16.15 Biosynthesis of O-linked oligosaccharide units on glycoproteins of the O, A, and B blood group substances. 

Scheme 6. Biosynthesis of Blood-group Substances. (The structure of the proximal portion is shown in a simplified form. According to Lloyd and Kabat, two chains are linked to 0-3 and 0-6 of the /J-D-galactose residue comprising the nonreducing, terminal residue in the sequence at the top of the Scheme. Only the chains linked to 0-3 are shown here.)...

Fig. 13. Possible genetic pathways for the biosynthesis of ABH blood group substances (Adapted from Watkins, 1966b). Note The O (Bombay) red cells fail to react with anti-A, anti-B, and anti-H.

A review of complex carbohydrates, which includes a discussion of the structures, isolation, biosynthesis, and functions of glycoproteins, glycosaminoglycans, and blood-group substances, has appeared. The structures of the carbohydrate moieties found in glycoproteins from such diverse sources as fungal and mam-rhalian cells have been compared. ... 

---