Enzymes from Human Gastric Mucosa Conferring Blood‐Group A and B Specificities upon Erythrocytes

Abstract

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...

Qualitative Differences in the N -Acetyl-D-galactosaminyltransferases Produced by Human A 1 and A 2 Genes

“…The N-acetyl-D-galactosaminyltransferase determined by the blood group A gene has been found in soluble form in human milk (1,2) and tnembrane-bound in human submaxillary gland (3), human gastric mucosa (4,5), hog submaxillary gland (6,7), and hog gastric mucosa (8)(9)(10). This transferase has been found recently in human ovarian cyst linings and fluids (11).…”

Enzymatic Conversion of Human Blood‐Group‐O Erythrocytes into A2 and A1 Cells by α‐N‐Acetyl‐d‐galactosaminyl Transferases of Blood‐Group‐A Individuals

“…Since the same gene appears to specify blood-type-A of erythrocytes as well as of body secretions [2], the gene-dependent enzyme must be able to transfer a-acetylgalactosaminyl residues to bloodgroup-A precursor molecules of glycolipid as well as of glycoprotein nature. In a previous investigation it has been shown that an enzyme, which was obtained from the gastric mucosa of group-A individuals and was found to transfer acetylgalactosamine residues onto water-soluble blood-group substances, was also capable of conveying blood-group-A specificity upon 0-erythrocytes [3]. Red cells of bloodgroup 0, when incubated with UDP-N-acetyl-Dgalactosamine in the presence of this enzyme, acquired the serological characteristics of A,-cells.…”

Localization of blood group antigens in human pancreas with lectin-horseradish peroxidase conjugates.

“…According to the hypothesis proposed by Watkins and Morgan (32,33), addition of the specific sugar to the H antigen yields A or B antigen. The isolation of specific glycosyltransferases from human tissues, which transform H antigen to A or B antigen, supported their hypothesis (23,25,34) . The production of precursor H antigen without subsequent transformation into the complete A or B specificity and independent production of either A or B antigen in AB individuals could be due to a lack of the specific glycosyltransferases or lack of specific sugar.…”