Glucansucrases are promising enzymatic tools for the synthesis of α-glucans with different structural and physicochemical properties from sucrose. These α-glucans have been found to have a variety of commercial applications in food, medicine, and biomaterials, particularly in the development of filled sweeteners, prebiotics, and dough improvers. The discovery of other subfamilies of the glycoside hydrolase family 70 (GH70) extended the reaction substrate to starch and dextrin, increased the variety and composition of glycosidic bonds in the product, and developed the scope for synthesizing novel α-glucans. Based on sequence comparisons and conformational analysis, it was found that the glycosidic bond composition, molecular weight, and degree of branching of the products were altered by mutation or modification of key amino acid residues. GtfB, GtfC and GtfD are evolutionary intermediates of dextransucrase (GtfA) and GH13. This paper introduces the classification of α-glucan and common GH70 members, analyzes key advances in enzyme conformational relationships, and outlines the rational design of more efficient, stable, and diverse α-glucan synthesis tools using enzyme engineering techniques.