CAT and Parkinson disease: Although the pathways and mechanisms of PD are still unclear, the finding of elevated levels of lipids, proteins, and oxidized nucleic acids, along with reduced levels of endogenous antioxidant systems such as SOD, catalase, reduced glutathione (GSH), and glutathione peroxidase in the substantia nigra of PD patients suggests that ROS, RNS, and OS play a role in the process [5, 17].