In this context, PD enzymes are the ATPase ATP13A2 encoded by a gene at the PARK9 locus, several GTPases, including the small GTPase RAB7L1, and leucine-rich repeat kinase 2 (LRRK2) which functions as a kinase and GTPase (Greggio, 2012; Taymans, 2012). Here, ATP13A2 is linked to Parkinson disease.