The presence of a-L-fucosyltransferases in human serum of different ABO, secretor and Lewis blood-group phenotypes was investigated with guanosine diphosphate fucose as the sugar donor and low-molecular-weight oligosaccharides, or a macromolecular glycoprotein, as acceptors. I n contrast to the a-2-~-fucosyltransferases in human milk, submaxillary glands and stomach mucosa that occur only in ABH secretors, an enzyme that transfers L-fucose to the C-2 position of nonreducing /3-galactosyl residues was found in the serum of all normal ABO donors irrespective of their ABH secretor-nonsecretor status. The only sera in which the a-2-~-fucosyltransferase was not demonstrable were three examples of the blood group Bombay Oh phenotype and one example of the Bh phenotype. I n the present paper the distribution of a-2,-3, and -4-L-fucosyltransferases in human serum from donors of different ABO, secretor and Lewis bloodgroup phenotypes is reported.[ 15 -171.

Enzyme preparations obtained from human gastric mucosa microsomes are able to provide human erythrocytes with blood-group A and B specificities, the newly conferred serological properties being dependent on the blood-group of the tissue donor. The time-course and the extent of the enzyme-catalyzed change in antigenic properties of the erythrocytes were assessed by the serum absorption method.The enzyme preparation from gastric mucosa of group A, individuals, when incubated with 0 or B erythrocytes in the presence of UDP-acetylgalactosamine, rendered them agglutinable by anti-A serum. The enzymatically converted erythrocytes behaved like A, cells. After treatment with enzyme from B individuals and UDP-galactose, 0, A, and A, erythrocytes could be agglutinated by anti-B serum. When the enzymes from A, and B individuals were allowed to act together upon 0 erythrocytes in the presence of UDP-acetylgalactosamine and UDPgalactose, the red cells became susceptible to agglutination with both anti-A and anti-B serum. The blood-group specificity of red cells was not changed upon exposure to microsomal extracts from 0 individuals.The group A and B specificities of red blood cells are determined by the presence of specific glycolipids and glycoproteins in the erythrocyte stroma [l, 21. The serological properties of both glycolipids and glycoproteins reside in their carbohydrate moieties. Due to difficulties in purification, the structure of the group-specific glycolipids which occur in the cell wall of erythrocytes is not yet known in detail [3]. There is, however, good evidence that their serological determinants are closely similar to those of the water-soluble blood-group substances found in various body secretions. The structure of the carbohydrate moieties of these water-soluble glycoproteins is fairly well established [4,5]. Terminal a-N-acetyl-D-galactosamine residues and a-D-galaCtose residues are responsible for the blood-group A and B specificities, respectively. It has been proposed that A and B substances are formed by enzymatic attachment of the antigenically determinant terminal sugar residues to blood-group H substance which serves as a common precursor [6].Enzymes capable of transferring N-acetylgalactosamine from UDP-acetylgalactosamine to watersoluble blood-group H substance [7-91, hog submaxillary glycoproteins [ 101 and several suitable oligosaccharides [1 1 -131 were recently found in human and animal tissues having blood-group A specificity. The occurrence of such enzymes was described for hog and human gastric mucosa For genetical reasons it is likely that the N-acetylgalactosaminyl and galactosyl transferases which have been found to convert soluble precursors to A and B specific substances are also capable of transferring the serologically determinant glycosyl residues to cell-bound precursor substances of both glycoprotein and glycolipid nature. Preliminary evidence in favour of this hypothesis has recently been reported. When the N-acetylgalactosaminyl transferase from hog gastric mucosa was allow...

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The contribution of blood-group-active glycolipids and glycoproteins to the blood-group-ABH character of human erythrocytes was investigated. For that purpose the blood-group-H sites of human 0 cells were converted in vitro into group-A sites by transfer of a-N-acetyl-~-['~C]galactosamine residues with the aid of the blood-group-A gene-dependent a-N-acetylgalactosaminyl transferase prepared from human A1 plasma. Upon partition of the red cell membranes between water and organic solvent, about 5 % of the label was found in the organic phase and about 20 % in the water phase, thus reflecting the distribution of blood-group antigenic sites between glycosphingolipids with short carbohydrate chains and polyglycosylceramides, respectively. The fact that about 70 % of the radioactivity remained tightly bound to the membranes and could only be released by treatment with pronase provided good evidence that the bulk of blood-group-H determinants is bound to glycoprotein material. Following these results it can thus be assumed that blood-group-ABH activity of human erythrocytes is determined preferentially by group-specific glycoproteins rather than glycolipids.