Substrate recognition of the catalytic α-subunit of glucosidase II from Schizosaccharomyces pombe.
The recombinant catalytic α-subunit of N-glycan processing glucosidase II from Schizosaccharomyces pombe (SpGIIα) was produced in Escherichia coli. The recombinant SpGIIα exhibited quite low stability, with a reduction in activity to <40% after 2-days preservation at 4 °C, but the presence of 10% (v/v) glycerol prevented this loss of activity. SpGIIα, a member of the glycoside hydrolase family 31 (GH31), displayed the typical substrate specificity of GH31 α-glucosidases. The enzyme hydrolyzed not only α-(1→3)- but also α-(1→2)-, α-(1→4)-, and α-(1→6)-glucosidic linkages, and p-nitrophenyl α-glucoside. SpGIIα displayed most catalytic properties of glucosidase II. Hydrolytic activity of the terminal α-glucosidic residue of Glc 2 Man 3 -Dansyl was faster than that of Glc 1 Man 3 -Dansyl. This catalytic α-subunit also removed terminal glucose residues from native N-glycans (Glc 2 Man 9 GlcNAc 2  and Glc 1 Man 9 GlcNAc 2 ) although the activity was low.
Okuyama M, Miyamoto M, Matsuo I, Iwamoto S, Serizawa R, Tanuma M, Ma M, Klahan P, Kumagai Y, Tagami T, Kimura A