STUDY OF THE Α‐N‐ACETYLGALACTOSAMINYLTRANSFERASE IN SERA AND RED CELL MEMBRANES OF HUMAN a SUBGROUPS

Abstract

SUMMARY The product of the A blood group gene in the erythrocyte membrane and serum from ‘weak A’ variants was investigated using low and high molecular weight acceptors and compared with common A1 and A2 blood samples. A reduced enzyme activity was detected, but only in some of the A variants, namely the A3 (eight out of eleven), Am or Ay samples. Other sera from A3 (three out of eleven), Ax, Aend or Ael individuals were apparently devoid of enzyme activity. A kinetic study by temperature inactivation of A blood group sera also showed that A enzymes are more labile than B enzymes from BI or BII sera. Moreover, in one case (A3 sample Del.), a very fast inactivation of the A enzyme was observed, suggesting the occurrence of a variant enzyme qualitatively different from the others so far studied. The erythrocyte membrane preparations from all A variants contained no detectable A enzyme activity except for the A1 and A2 samples, the former being three to five times more active than the latter. The B enzyme activities from four samples of B RBC tested were comparatively stronger than the A enzyme activity of A1 RBC. The results were discussed and it was suggested that the synthesis and/or the secretion of the A enzyme in the organism is not uniform from one tissue to another, but could depend on which of the ‘weak A’ alleles or modifier genes is involved.

ABH glycosyltransferase levels in sera and red cell membranes from Hz and Hm variant bloods

“…Reagents and methods used to estimate A, B and H glycosyltransferases in sera and RBC membranes have been described [ 12,19,20] …”

“…Indeed, the A transferase of Am sera is only 30-50% as active as controls [ 191 but is completely absent or inactive in RBC [20] which indicates that Am phenotypes arise either from a modifier or a rare allele at the ABO locus.…”

Activity of 2‐α‐L‐fucosyltransferase in human sera and red cell membranes A study of common ABH blood donors, rare ‘Bombay’ and ‘Parabombay’ individuals

“…Enzyme assays in RBC ghosts: A and B enzymes in erythrocyte membrane were estimated as described by Cartron et al [30]. The 2~-L-fucosyltransferase from RBC was performed by adding the following components in total vol.…”

Genetics of ABO, H, Lewis, X and Related Antigens

“…The A enzymes product of these A genes have different optimum pH values and different isoelectric points. Both A enzymes transfer N-acetylgalactosamine to the H type 1 and H type 2 structures, but the A] enzyme is more efficient than the A2 enzyme [9,25]. In addition to the quantitative difference in the amount of A epitopes found in Ai and A2 red cells, the Ai erythrocytes also express A type 3 [26] and A type 4 [27] epitopes, which have not been found on A2 erythrocytes.…”