This is the N-terminal domain found in glycoside hydrolase family 131 (GH131A) protein observed in Coprinopsis cinerea. GH131A exhibits bifunctional exo-beta-1,3-/-1,6- and endo-beta-1,4 activity toward beta-glucan. This domain is catalytic in nature though the catalytic mechanism of C. cinerea GH131A is different from that of typical glycosidases that use a pair of carboxylic acid residues as the catalytic residues. In the case of GH131A, Glu98 and His218 may form a catalytic dyad and Glu98 may activate His218 during catalysis [1].

1: Crystal structure of the N-terminal domain of a glycoside hydrolase family 131 protein from Coprinopsis cinerea. Miyazaki T, Yoshida M, Tamura M, Tanaka Y, Umezawa K, Nishikawa A, Tonozuka T; FEBS Lett. 2013;587:2193-2198. PMID:23711369