Aberrant blood group activities of ABH substances from human gastric linings

Recently it was shown that enzymes specific to blood groups A and B have an inherent function overlapping each other and that under certain in vitro conditions they exhibit a weak activity to synthesize aberrant blood group substance. In an attempt to examine the results of the in vivo activities of these enzymes, we investigated the activities of blood group substances from human materials. After partial purification and concentration of blood group substances, weak B activities were shown in some materials from group A individuals, especially from gastric linings, and weak A activities in group B materials. Weak A and/or B activities in substances from group O persons were recognized. The reciprocal activities were specifically destroyed by blood group-decomposing enzymes with enhancement of H activity. These results suggest that the A and B enzymes can utilize the reciprocal nucleotide substrate even under in vivo conditions. The results support the inference that blood group O gene-mediated proteins exist and have activities to synthesize A and B structures.