KYNU and Parkinson disease: For example, Heilman et al.(2020) found that plasma levels of 3-OH-KYN were significantly elevatedin PD patients, most of which did not exhibit dyskinesia.14 The authors attributed this to reduced activityof the enzyme kynureninase (EC 3.7.1.3), which catalyzes the conversionof 3-OH-KYN into 3-OH-AA.