An extensive investigation of some enzymes described to be upregulated or downregulated in PD was made – adenylate kinase (AK), adenine phosphoribosyltransferase (APRT), ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1), nucleoside-diphosphate kinase 3 (NDK3), purine nucleoside phosphorylase 1 (PNP1), and ecto-5’-nucleotidase (NT5E). The gene discussed is PTPN13; the disease is Parkinson disease.