There are conflicting views on the nature of subgroups A, and A2 of blood group A, One holds that the same determinants are present on either, but that there are fewer determinants on A2 than on A, erythrocytes. Soluble A2 and A, substances would thus have the same kinds of determinants, but in different numbers. The A1 and A2 transferases are different enzymes, but the A2 enzyme is less effici...