The temperature dependence of the kinetic parameters of the aspartase-catalyzed reaction has been examined in the direction of deamination. The pK1values at 37$^{circ}C$, 25$^{circ}C$, 16$^{circ}C$ and 7$^{circ}C$ were 6.2 $pm$ 0.1, 6.3 $pm$ 0.1, $6.7{pm}0.3$ and 6.9 $pm$ 0.3, respectively. On the other hand, the pK2 values at 37$^{circ}C$,25$^{circ}C$, 16$^{circ}C$ and 7$^{circ}C$ were 8.1 $pm0.2$, 8.3 $pm$ 0.2, 8.2 $pm$ 0.3 and 8.0 $pm$ 0.2,respectively. The enthalpy of ionization, DHion, calculated from the slope of pK1, are 6.0 $pm$ 0.3 kcal/mol. These results validate the prediction that aspartase requires a histidine residue for a general base, and a cysteine (or having a carboxyl functional group) for a general acid.