In the substantia nigra of PD patients, significant downregulation was mainly seen in N-acetylgalactosaminyltransferases (GANTL-5, -9, -11, -14, which are predominantly involved in O-glycosylation, were decreased by −14.65, −3.64, −3.91, and −8.59-fold, respectively), in N-acetylglucosaminyltransferases (MGAT-4B, -4C, and -5B, which play a role in the branching of N-glycans), in sialidases (neuraminidases NEU-1 and -2) and sialyltransferases (ST8SIA-3, -4, and -6, which are mainly regulating the formation of PSA). Here, NEU1 is linked to Parkinson disease.