Separation of the M and N blood-group antigens of the human erythrocyte

Treatment of washed human erythrocytes with the proteolytic enzyme pronase rapidly releases bound sialic acid from the membrane. The amount of bound sialic acid liberated is equal to the amount of free sialic acid which is released from this cell by neuraminidase (EC 3.2.1.18).

The bound sialic acid, liberated by pronase, was shown to be present in glycopeptides possessing M and N blood-group activity towards rabbit and human antisera. Using an MN active glycopeptide fraction, purified on Sephadex G-25, it has been possible by using DEAE-Sephadex to separate for the first time the M antigen from the N antigen. These glycopeptides which were obtained in a high degree of purity were shown to possess different carbohydrate compositions.