This domain is found at the N-terminal end of protein members of the glycoside hydrolase family 123, including N-acetylgalactosaminidase from Clostridium perfringens. This enzyme removes specific terminal N-D-acetylgalactosamine from glycosphingolipids. This domain folds into a twisted beta-sandwich that consists of two 5-stranded beta-sheets, two small beta-strands and four small alpha-helices [1].

1: The Details of Glycolipid Glycan Hydrolysis by the Structural Analysis of a Family 123 Glycoside Hydrolase from Clostridium perfringens. Noach I, Pluvinage B, Laurie C, Abe KT, Alteen MG, Vocadlo DJ, Boraston AB; J Mol Biol. 2016;428:3253-3265. PMID:27038508

2: Structural and mechanistic insights into a Bacteroides vulgatus retaining N-acetyl-beta-galactosaminidase that uses neighbouring group participation. Roth C, Petricevic M, John A, Goddard-Borger ED, Davies GJ, Williams SJ; Chem Commun (Camb). 2016;52:11096-11099. PMID:27546776