GAPDH and Parkinson disease: Moreover, as illustrated in Fig. 9, the observations indicating a reduced expression of the ubiquitous glycolytic enzyme, GAPDH, and of the astrocytic serine transporter, ASCT1, in the rPut of MPTP-treated monkeys, hold substantial significance in light of the emerging understanding of disrupted energy homeostasis and astrocyte dysfunction in the pathophysiology of PD.