Histo-blood group A and B transferases, their gene structures, and common O group gene structures

Abstract

The human ABO antigens are the most important blood groups in transfusion and transplantation medicine (Storry and Olsson 2009; Yamamoto et al. 2012). Histo-blood group A and B antigens are produced by UDP-GalNAc: H-a3GalNAc transferase (GTA; EC 2.4.1.40) and UDP-Gal: H-a3Gal transferase (GTB; EC 2.4.1.37), respectively (Fig. 44.1). GTA and GTB are retaining enzymes and are members of GT family 6 in the CAZy database. The minimal acceptor is an H-disaccharide (αFuc1→2βGal) on a glycoprotein, glycolipid, or free oligosaccharide. Depending on the structure of the H precursor, four types of A antigen and three types of B antigen have been identified (Fig. 44.2). Type-3 chain A, i.e., repetitive A, is present only as a glycosphingolipid in A1-erythrocytes but not in A2-erythrocytes (see Chap. 69, “ST6 N-Acetylgalactosaminide Alpha-2,6-Sialyltransferase 5,6 (ST6GALNAC5,6)"; “Cross-References”). The corresponding “repetitive B” is absent or unknown. Type-4 chain A (globo-A) is also expressed in A1-erythrocytes but not in A2-erythrocytes. Type-4 chain B (globo-B) is not known in erythrocytes; however, both globo-A and globo-B are highly expressed in other organs, particularly the kidney and surogenital epithelia. The distribution patterns of these isotypes of A and B antigens, and their patterns during development, have been reviewed (Hakomori 1981; Oriol et al. 1986; Clausen and Hakomori 1989; Oriol 1995). In this chapter, only allelic structures of A and B transferases, and the allele for the common O blood group gene, are described. Alleles for variants are described in Chap. 69, “ST6 N-Acetylgalactosaminide Alpha-2,6-Sialyltransferase 5,6 (ST6GALNAC5,6)" (see “Cross-References”).