According to whole-genome sequencing, Aspergillus niger produces multiple enzymes of glycoside hydrolases (GH) 31. Here we focus on a GH31 alpha-glucosidase, AgdB, from A. niger. AgdB has also previously been reported as being expressed in the yeast species, Pichia pastoris; while the recombinant enzyme (rAgdB) has been shown to catalyze tranglycosylation via a complex mechanism. We constructed an expression system for A. niger AgdB using Aspergillus nidulans. To better elucidate the complicated mechanism employed by AgdB for transglucosylation, we also established a method to quantify glucosidic linkages in the transglucosylation products using 2D NMR spectroscopy. Results from the enzyme activity analysis indicated that the optimum temperature was 65 degrees C and optimum pH range was 6.0-7.0. Further, the NMR results showed that when maltose or maltopentaose served as the substrate, alpha-1,2-, alpha-1,3-, and small amount of alpha-1,1-beta-linked oligosaccharides are present throughout the transglucosylation products of AgdB. These results suggest that AgdB is an alpha-glucosidase that serves as a transglucosylase capable of effectively producing oligosaccharides with alpha-1,2-, alpha-1,3-glucosidic linkages.