Probable Biosynthetic Pathway for the Synthesis of the B Antigen from B(h) Variants

Abstract

Red cells and serum from two B(h) variants (B+H-cells) have been investigated for B and H blood group glycosyltransferases. The H enzyme could not be detected using either type 1 or type 2 chain acceptors. The B enzyme was present in normal amount when 2'-fucosyllactose was used as substrate, neither 6'-fucosyllactose nor 6'-fucosyllactosamine could act as acceptors for the B enzyme. Upon treatment of the B(h) red cells by the B-degrading enzyme from Trichomonas foetus the B antigen was destroyed while H determinants were uncovered (B-H+ cells). The cells thus treated could be further converted into A+H- red cells by the action of the A transferase from human blood group A serum. Previous treatment of the B-H+cells by the H-degrading enzyme from T. foetus, however, led to B-H- erythrocytes and prevented their conversion into A red blood cells by the A enzyme. The results clearly demonstrate that, as found in normal B individuals, the B antigen from B(h) cells is built up from the H precursor and provide additional evidence that H is not a completely silent gene in B(h) individuals.

ABO, H, and Lewis Systems

“…[438] demonstrated that H is the precursor of B on the cells of a B h individual. Consequently, the small amount of H produced is completely converted to A or B. Mulet et al .…”

Immunochemistry of the Lewis blood‐group system

“…od->3/4 and ctl-~2 fucosidase were purified from an ultrasonic extract of Trichomonas foetus by fractionation on Sepharose 4B followed by chromatography on DEAE-cellulose [13], the enzymes being eluted with 0.7 M and 0.15 M KC1, respectively.…”