Blood Group Antigens and the Enzymes Involved in their Synthesis: Past and Present
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Chemical studies on the antigens associated with the ABO system were initiated in the early years of the century but progress was limited by the paucity of techniques then available for the study of complex macromolecules. By the 1940s the secreted blood group substance’s were known to be polysaccharide-amino acid complexes but it was not until the 1950s that the nature of the precise differences which give rise to ABH and Lewis blood group specificities began to be recognized (1). Three main lines of attack were particularly useful in providing information about the specific structures. The first involved indirect methods of inhibition of haemagglutination and precipitation, and of the enzymatic inactivation of the specific substances, by simple sugars and oligosaccharides of known structure. The second method involved the examination of the chemical changes that occur when the serological activity is destroyed by a specific enzyme. The third method was the direct isolation and identification of serologically active fragments from the products of partial degradation of the macromolecules (2). A combination of these methods allowed the now well established carbohydrate structures of the A,B,H,Lea and Leb determinants to be elucidated.