PON1 and Parkinson disease: Furthermore, OPs are more strongly associated with PD in patients with certain genetic variations in paraoxonase 1 (PON1), aldehyde dehydrogenase (ALDH2), and nitric oxide synthase (NOS1) (Benmoyal-Segal et al., 2005; Fitzmaurice et al., 2014; Paul et al., 2016).