Dear Editor,rnThree polyamines,putrescine,sper-midine,and spermine,are tightly regu-lated and are synthesized from arginine,ornithine,and methionine(Miller-Fleming et al.,2015;Figure 1A).Polyamine levels are increased in the red blood cells of amyotrophic lateral sclerosis and Parkinson\'s disease (PD)patients (Miller-Fleming et al.,2015).Sulfur amino acid catabolism regulated by the molybdopterin synthase associ-ating complex prevents onset of early events in PD and Alzheimer\'s disease(Suganuma et al.,2018).MPT synthase,a heterodimer of MOCS2A and MOCS2B encoded by MOCS2,is essential for the biosynthesis of molybdenum cofactor(Moco),which is required for the activ-ity of xanthine dehydrogenase (XDH)(Schwarz et al.,2009;Suganuma et al.,2018).XDH is the single transcribed form of xanthine oxidoreductase,which catalyzes the terminal two reactions in purine degradation,i.e.oxidation of hy-poxanthine to xanthine and oxidation of xanthine to uric acid (Schwarz et al.,2009;Figure 1A).Defects in any step of Moco biosynthesis lead to Moco defi-ciency (MoCD),characterized by rapid progression of neurodegeneration and lethality in early childhood (Schwarz et al.,2009).Notably,increases in the levels of inosine,hypoxanthine,and xanthine have been found in both MoCD and Huntington\'s disease (Toczek et al.,2016;Suganuma et al.,2018).Therefore,links between nucleotide me-tabolism and polyamine metabolism may contribute to the pathogenesis of these diseases.