Structural insight into a yeast maltase—The BaAG2 from blastobotrys adeninivorans with transglycosylating activity

Karin Ernits, Christian Kjeldsen, Karina Persson, Eliis Grigor, Tiina Alamäe, Triinu Visnapuu*

*Corresponding author for this work

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An early-diverged yeast, Blastobotrys (Arxula) adeninivorans (Ba), has biotechnological potential due to nutritional versatility, temperature tolerance, and production of technologically ap-plicable enzymes. We have biochemically characterized from the Ba type strain (CBS 8244) the GH13-family maltase BaAG2 with efficient transglycosylation activity on maltose. In the current study, transglycosylation of sucrose was studied in detail. The chemical entities of sucrose-derived oligosaccharides were determined using nuclear magnetic resonance. Several potentially prebiotic oligosaccharides with α-1,1, α-1,3, α-1,4, and α-1,6 linkages were disclosed among the products. Trisaccharides isomelezitose, erlose, and theanderose, and disaccharides maltulose and trehalulose were dominant transglycosylation products. To date no structure for yeast maltase has been deter-mined. Structures of the BaAG2 with acarbose and glucose in the active center were solved at 2.12 and 2.13 Å resolution, respectively. BaAG2 exhibited a catalytic domain with a (β/α)8-barrel fold and Asp216, Glu274, and Asp348 as the catalytic triad. The fairly wide active site cleft contained water channels mediating substrate hydrolysis. Next to the substrate-binding pocket an enlarged space for potential binding of transglycosylation acceptors was identified. The involvement of a Glu (Glu309) at subsite +2 and an Arg (Arg233) at subsite +3 in substrate binding was shown for the first time for α-glucosidases.
Original languageEnglish
Article number816
JournalJournal of Fungi
Issue number10
Number of pages24
Publication statusPublished - 2021


  • Acarbose
  • Crystal struc-ture
  • Erlose
  • Glycoside hydrolase
  • Isomalto-oligosaccharides
  • Isomelezitose
  • Molecular replacement
  • Nuclear magnetic resonance
  • Trehalulose
  • α-glucosidase


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