DDC and Parkinson disease: Therefore, the subnetwork was considered to be an important subset of PD pathogens including DRD2, SLC18A2, TH, DDC, SLC6A3, SNCA, NR4A2, KCNJ6, and ACHE, and they were involved in molecular function of protein binding with signaling pathways including carbon metabolism, metabolic pathway, and biosynthesis of antibiotics.