HAD activities of WT HN3, WT HN1, and amino acid-substituted HN3 glycoproteins for 23SD-RBCs. 23SD-RBCs were prepared by 23SD treatment of native RBCs for 30 (gray column), 45 (hatched column), or 60 min (empty column) at 37 °C. HAD activities of HN3 and HN1 glycoproteins for native RBCs (filled column) and 23SD-RBCs are represented as relative percentages to those of WT HN3 glycoprotein and WT HN1 glycoprotein for native RBCs, respectively.