H-deficient blood groups of Reunion Island. III. alpha-2-L-fucosyltransferase activity in sera of homozygous and heterozygous individuals.

Small amounts of H-enzyme activity (from 500 to 1,280 counts per minute [cpm]) were detected in sera of white H-deficient individuals (h/h; Reunion phenotype), while no significant H activity (less than 500 cpm) could be detected in sera of Indian H-deficient individuals (h/h; Bombay phenotype). The H-enzyme levels of the unaffected members of H-deficient pedigrees showed an H-related dosage effect. Heterozygous H/h individuals had only half as much H activity in sera (17,000 +/- 3,400 cpm) compared with homozygous H/H individuals (31,600 +/- 3,700 cpm). Data suggesting interactions between the H enzyme and the other gene specified glycosyltransferases working on the same oligosaccharide chains carrying combined ABH and Lewis antigens are analyzed in terms of their possible genetic or biochemical origin.