This invention relates to enzymatic removal of type A and B antigens from blood group A, B, and AB reactive cells in blood products, and thereby converting these to non-A and non-B reactive cells. The invention further relates to using unique αN-acetylgalactosaminidases and α-galactosidases with superior kinetic properties for removing the immunodominant monosaccharides of the blood group A and B antigens and improved performance in enzymatic conversion of red blood cells. The preferred unique α-N-acetylgalactosaminidases and α-galactosidases exhibit the following characteristics: (i) exclusive, preferred or no less than 10% substrate specificity for the type A and B branched polysaccharide structures relative to measurable activity with simple mono- and disaccharide structures and aglycon derivatives hereof; (ii) optimal performance at neutral pH with blood group oligosaccharides and in enzymatic conversion of cells; and (iii) a favorable kinetic constant Km with mono- and oligosaccharide substrates. The conversion methods of the invention use significantly lower amounts of recombinant glycosidase enzymes than previous and result in complete sero-conversion of all blood group A and B red cells.