The Gfo/Idh/MocA family enzyme DgpA was known to catalyze the regiospecific oxidation of puerarin to 3"-oxo-puerarin in the presence of 3-oxo-glucose. Here, we discovered that D3dgpA, <i>dgpA</i> cloned from the human gut bacterium <i>Dorea</i> sp. MRG-IFC3, catalyzed the regiospecific oxidation of various <i>C</i>-/<i>O</i>-glycosides, including puerarin, in the presence of methyl β-D-3-oxo-glucopyranoside. While <i>C</i>-glycosides were converted to 3"- and 2"-oxo-products by D3dgpA, <i>O</i>-glycosides resulted in the formation of aglycones and hexose enediolone from the 3"-oxo-products. From DFT calculations, it was found that isomerization of 3"-oxo-puerarin to 2"-oxo-puerarin required a small activation energy of 9.86 kcal/mol, and the <i>O</i>-glycosidic bond cleavage of 3"-oxo-products was also thermodynamically favored with a small activation energy of 3.49 kcal/mol. In addition, the reaction mechanism of D3dgpA was discussed in comparison to those of Gfo/Idh/MocA and GMC family enzymes. The robust reactivity of D3dgpA was proposed as a new general route for derivatization of glycosides.