Nitrogen-Rich Molybdenum Nitride with Intrinsic CD39 Nucleotidase Activity.

CD39 is one of the important nucleotidases to adjust extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentration. However, the enzyme mimics to simulate the activity of CD39 still remains to be explored. Herein nitrogen-rich molybdenum nitride (Mo₅N₆) nanosheets are explored to possess CD39-like activity, which are able to catalyze the hydrolysis of the high-energy phosphate bonds (HEPBs) in ATP and ADP but not the common phosphate bonds in adenosine monophosphate (AMP). The catalytic hydrolysis of the phosphate bond over Mo₅N₆-700 nanosheets is first investigated using para-nitrophenyl phosphate as the model substrate and then the CD39-like activity is further explored and verified by ³¹p NMR spectroscopy. Mo⁴⁺ on the surface of Mo₅N₆-700 nanosheets are the catalytic active sites. Using ATP as the model substrate, the K_m and V_max values of CD39-like activity at optimal pH 9.0 are 3.2 µmol L^-1 and 18.5 µmol L^-1 h^-1, respectively. The CD39-like activity of Mo₅N₆-700 nanosheets enabled the down-regulation of intracellular ATP concentration to a larger degree for cancer cells than normal cells, which makes Mo₅N₆-700 nanosheets a potential therapeutic reagent for cancers.