抄録
1. The blood group A-decomposing enzyme preparation from Clostridium tertium A which had been adsorbed on a DEAE-Sephadex column was eluted in two portions which had A-decomposing activity. The fast eluted fraction (Fr. 4) had activity of N-deacetylase, and when incubated with A substance, it abolished the A-activity, which was restored by N-acetylation. It did not abolish the reactivity of A substance to anti-A+B agglutinin of group O serum or of plant seed, nor it affected the O (H) -activity. The slow eluted fractions (Fr. 31- 34), acting on A substance, destroyed its A-activity and reactivity to anti-A+B agglutinin, and enhanced O (H) -activity. In this case, the lost A-activity of the ènzyme treated substance did not restore by N-acetylation.
2. Antiserum, prepared by immnizing the rabbit or chicken with Fr. 4-treated A substance, contained an antibody which reacted with Fr. 4 -treated blood group A red cells but not with untreated blood group A or B red cells and blood group substances, and which was specifically inhibited by D-galactosarnine. When incubated with Fr. 31-34 enzyme, the Fr. 4- treated A substance or red cells lost reactivity to this antiserum, while the O (H) -activity was enhanced.
3. Fr. 4 of A-decomposing enzyme did not liberate reducing sugar from A substance or blood group A red cells, whereas Fr. 31-34 of A-decomposing enzyme freed galactosamine (and a small amount of N-acetylgalactosainine) from them. These results show that Fr. 4 exerts N-deacetylase action on N-acetylgalactosaminoyl residue, which is determinant of the A specificity, and that Fr. 31-34 possesses the activity of galactosaminidase and/or partially of N-acetylgalactosaminidase as well as the activity of N-deacetylase.
