Purification and Characterization of [alpha]-N-Acetylgalactosaminidases I and II from the Starfish Asterina amurensis

Two α-N-acetylgalactosaminidases, α-N-acetylgalactosaminidase (α-GalNAcase) I and II, were purified from the digestive organ of starfish. Purified α-GalNAcase I and II gave nearly single protein bands on SDS-polyacrylamide gel electrophoresis, individually. Even the final preparation of α-GalNAcase I contained α-galactosidase activity, while α-GalNAcase II was almost free from that activity with p-nitrophenyl and 4-methylumbelliferyl α-N-acetylgalactosaminides as substrates. α-GalNAcase I and II both hydrolyzed terminal α-N-acetylgalactosaminyl linkages of the natural compounds investigated: Forssman hapten glycolipid, blood group A active oligosaccharide and GalNAc-α1-O-serine. On the other hand, oligosaccharides, and glycolipid containing α-galactosyl terminals were hydrolyzed by α-GalNAcase I but not by α-GalNAcase II. The substrate specificities and other enzymatic properties of α-GalNAcase I were similar to those of human placental α-GalNAcase, but distinct from α-GalNAcase II.