Glycosyltransferases A and B: Four Critical Amino Acids Determine Blood Type

Abstract

Human A, B, and O blood type is determined by the presence or absence of distinct carbohydrate structures on red blood cells. Type O individuals have α-fucose(1→2)galactose disaccharides [O(H) structures] on their cell surfaces while in type A or B individuals, the O antigen is capped by the addition of an α- N-acetylgalactosamine or α-galactose residue, respectively. The addition of these monosaccharides is catalyzed by glycosyltransferase A (GTA) or glycosyltransferase B (GTB). These are homologous enzymes differing by only 4 amino acids out of 354 that change the specificity from GTA to GTB. In this review the chemistry of the blood group ABO system and the role of GTA, GTB, and the four critical amino acids in determining blood group status are discussed.