**5. Conclusions**

According to the literature data, a non-conventional yeast *Blastobotrys* (*Arxula) adeninivorans* belonging to the basal group of Saccharomycotina diverged in the evolution of yeasts hundreds of millions of years before *Saccharomyces* and can be considered as a yeast species with deep phylogeny. The genome of *B. adeninivorans* encodes two putative α-glucosidases. In current work, one of them, *Ba*AG2, was produced in *E. coli* and characterized in detail. *Ba*AG2 was proven to be a maltase—hydrolysing α-1,4 and α-1,3 but not α-1,6 linkages in glucose-containing substrates. Interestingly*, Ba*AG2 was strongly and competitively inhibited not only by acarbose, a diabetes drug and a well-known inhibitor of α-glucosidases, but also by Tris. Importantly, at high maltose concentrations, *Ba*AG2 exhibited transglycosylating ability producing potentially prebiotic di- and trisaccharides: isomaltose, panose and maltotriose. Thus, *Ba*AG2 may have a biotechnological value. In contrast to yeast maltases, *Ba*AG2 showed exo-hydrolytic activity on starch, amylose, amylopectin and glycogen. *S. cerevisiae* maltase MAL62 assayed for comparison had only minimal ability towards these polymers and its transglycosylating activity was much lower.

**Supplementary Materials:** Supplementary file can be found at http://www.mdpi.com/1422-0067/21/1/297/s1.

**Author Contributions:** Conceptualization, T.A. and T.V.; Methodology, T.V., K.E., A.M., K.P. and K.V.; Validation, T.V., K.E. and T.A.; Formal Analysis, T.V., A.M., K.P. and K.E.; Investigation, T.V. A.M., K.V., K.P., K.E. and T.A.; Resources, T.A. and T.V.; Writing—original draft preparation, T.A. and T.V.; Writing—review and editing, T.A., T.V., K.E. and K.P.; Visualization, T.V., K.E., A.M., K.P. and T.A.; supervision, T.A. and T.V.; funding acquisition, T.A and T.V. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was funded by the Estonian Research Council (grant number PUT1050) to T.A. The article processing charge was covered by University of Tartu Feasibility Fund grant PLTMRARENG13 to T.V.

**Acknowledgments:** We thank V. Passoth (SLU, Uppsala, Sweden) for providing the *B. adeninivorans* strain, B. Svensson (DTU, Kongens Lyngby, Denmark) for providing amylose and amylopectin and H. Vija (NICPB, Tallinn, Estonia) for the services in sugar quantification.

**Conflicts of Interest:** The authors declare no conflict of interest.
