N-terminal catalytic domain of mainly uncharacterized eukaryotic proteins similar to alpha-mannosidases; glycoside hydrolase family 38 (GH38)
The subfamily of mainly uncharacterized eukaryotic proteins shows sequence homology with class II alpha-mannosidases (AlphaAMIIs). AlphaAMIIs possess a-1,3, a-1,6, and a-1,2 hydrolytic activity, and catalyze the degradation of N-linked oligosaccharides. The N-terminal catalytic domain of alphaMII adopts a structure consisting of parallel 7-stranded beta/alpha barrel. This subfamily belongs to the GH38 family of retaining glycosyl hydrolases, which employ a two-step mechanism involving the formation of a covalent glycosyl enzyme complex; two carboxylic acids positioned within the active site act in concert: one as a catalytic nucleophile and the other as a general acid/base catalyst.