Gene cloning and expression of a glucoside 3-dehydrogenase from Sphingobacterium faecium ZJF-D6, and used it to produce N-p-nitrophenyl-3-ketovalidamine.

In this study, we report the cloning and expression of a functional glucoside 3-dehydrogenase (G3DH) gene from Sphingobacterium faecium ZJF-D6. This gene is 1686 bp in length and encodes a peptide of 562 amino acids. The G3DH gene was successfully expressed in E. coli, and the recombinant enzyme could oxidize glucosides, galactosides and analogues at C-3 position. The sequence and multiple alignment analysis showed that the enzyme has highest identity with G3DHs from Paraglaciecola polaris LMG 21857, Aliiglaciecola lipolytica E3 and Halomonas sp. alpha-15. The recombinant G3DH was purified on Ni-NTA column and exhibited the highest activity at pH 7.6 and 30 °C. It was sensitive to acid and alkali, and showed well thermostability. The SfG3DH could oxidize a wild range of sugars. When recombinant E. coli BL21 cells were used as catalyst, a high rate of conversion to N-p-nitrophenyl-3-ketovalidamine was achieved, and no p-nitroaniline was detected. This process offers a promising approach to fulfill substrate of 3-ketovalidoxylamine A C-N lyase production.