where V0 represents the initial velocity, Vmax stands for the maximum reaction velocity, denotes the concentration of chromogenic agents, TMB, and Km signifies the Michaelis constant as previously reported in the literature . To do this, a series of experiments were carried out for the oxidation of different concentrations of TMB in different concentrations of 0.015-0.2 mM over the developed nanozymes. The oxidation reaction rate was then calculated in nM min -1 . Afterward, the Michaelis-Menten curve was plotted by plotting the rate as a function of TMB concentration. The results are shown in Figure . As can be seen in this figure, the rate of the oxidation process was increased by increasing the TMB concentration and then leveling off. Based on the Michaelis-Menten curve, a Vmax as high as 55. 5 nM min -1 was provided for the oxidase-like Ce/Fe-bimetallic nanozymes, revealing their high catalytic activity. Besides, the Km value was found to be about 0.05 mM. Moreover, Vmax/Km was calculated as a crucial indicator of enzyme catalytic efficiency, the results revealed a ratio of 1.10 ×10 -3 min -1 from the non-linear Michaelis-Menten curve.