In general, members of each GH family share common traits, and key residues involved in catalysis and structural stabilization are conserved within each family 5, 6. GH family 97 (GH97), as a unique GH family, was firstly discovered in 2005 4. Glycoside hydrolases (GHs) are a class of enzymes that can hydrolyze glycosidic bonds in carbohydrates, and glucoamylases are mainly distributed in GH15 and GH97 family according to the carbohydrate-active enzyme (CAZy) database ( ) 3. Glucoamylase (GA) (EC 3.2.1.3, α-l, 4-glucan glucohydrolase), one of the most extensively utilized enzymes in industry, cleaves α-1,4-glycosidic linkages and α-1,6-glycosidic linkages from the non-reducing end of oligosaccharide substrates and starch to release β- d-glucose 1, 2. Our study reveals that Ba 2+ or Sr 2+ may be involved in the catalytic mechanism of glucoamylase, laying the groundwork for a more complete knowledge of GH97 and its possible industrial application. These results imply that QsGH97a not only is a new member of GH97, but also has potential for industrial applications. The specific metal activity was initially revealed in glucoamylases, which is not found in other members. Additionally, the metal content of QsGH97a assay showed a high proportion of Sr 2+. Ca 2+ has little effect on the catalytic activity however, the activity can be substantially increased by 8–13 folds in the presence of Ba 2+ or Sr 2+. The biochemical characterization indicates that QsGH97a shows the optimal activity at 50 ☌ and pH 8.0. Sequence analysis and NMR results show that QsGH97a is classified into GH97a, and adopts inverting mechanism. In this study, a novel glucoamylase QsGH97a from Qipengyuania seohaensis SW-135 was cloned and expressed in E. It is critical to explore novel members to elucidate the catalytic mechanism and application potential of GH97 family. Only ten members of GH97 have been characterized so far. As an interesting glycosidase family, Glycoside hydrolase family 97 (GH97) contains α-glucosidase, α-galactosidase, and glucoamylase. Glycoside hydrolases (GHs), the enzymes that break glycosidic bonds, are ubiquitous in the ecosystem, where they perform a range of biological functions.
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