Characterization of N-Acetyl-Alpha-D-Galactosamidase from Clostridium Paraputrificum
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The antigenic determinants of the ABO blood group are glycolipids and glycoproteins on the erythrocyte membrane. Structurally. there exists a stem. known as the H stem. to which the immunodominant sugars are attached. In type 0 blood, the end of the H stem is the immunodominant sugar. In types A and B blood, on the other hand, immunodominant sugars have been added to the end of the H stem by way of enzyme action. Enzymes known as exoglycosidases have been discovered which are able to remove the immunodominant sugars of types A and B blood, thereby converting them to type 0. the universal blood donor type. Filtrates of Clostridium paraputrificum were found to have this ability and work is continuing on the purification of the enzyme. Specifically the enzyme, known as Azyme. is an N-acetylgalactosaminidase. Azyme is active with p-nitropheny1-2-acetamido-2-deoxy-alpha - D-galactopyranoside, which has been used as a synthetic substrate during research. The characteristics of Clostridium paraputrificum Azyme are: (1) an optimal pH around 6.0; (2) somewhat heat labile, 37°C, especially after longterm exposure, but quite stable at 4°C; and (3) mercuric ion significantly decreases the activity of the enzyme. although reducing agents were not seen to be necessary for preservation. The result of the enzyme's action on type A erythrocytes is the loss of A activity and the simultaneous appearance of H activity. The Azyme isolated from Clostridium paraputrificum is thought to be structurally equivalent to the Azyme isolated from Clostridium perfringens.