Comparative structural, biochemical and kinetic studies between thermostable and cold-adapted glucoamylases.

WAYLLACE, NATAEL M.; BUSI, MARIA VICTORIA; DIEGO FABIAN GOMEZ CASATI

Mendoza

Congreso; LVIII Reunion SAIB; 2022

SAIB

Glucoamylases (GAs, EC 3.2.1.3, glucan1,4-α-glucosidase) are hydrolytic enzymes also known as amyloglucosidases. GAsbelongs to the GH15 and GH97 families of glycoside hydrolases (www.cazy.org).These enzymes are exo-amylases that hydrolyze α-1,4 glycosidic bonds by thesuccessive removal of glucose residues from the non-reducing end of starch andrelated substrates, releasing β-D-glucose. In previous studies, we identifiedand characterized two novel GAs: TeGA, from Thermoanaerobacterethanolicus, a thermophilic anaerobic bacterium and SdGA, from Saccharophagus degradans, a marinebacterium which degrades different complex polysaccharides at high rate.  TeGA is a thermophilic enzyme while SdGA is acold-adapted enzyme. Srtucturally, these proteins are composed by an N-terminalGH15_N domain linked to a C-terminal catalytic domain (CD), found in the GH15family of glycosyl hydrolases. In this study we compared the global structure,catalytic residues, catalytic clefts and the flexibility of SdGA, TeGA and otherthermophilic, cold-adapted and psicrophilic enzymes. We identified somecharacteristics of cold-adapted GAs that would explain the adaptation of theseenzymes to low temperature.