CAT and Parkinson disease: In the NAC + SMC group, the Cat activity was also significantly higher than the PD group with an average of 32.60 ± 4.42 in serum and 2.49 ± 0.66 in brain tissue (P = 0.008 in serum and P = 0.005 in tissue; Fig. 4-E and Fig. 4-F).