Kinetic studies on the hydrogen peroxide elimination by cultured PC12 cells: rate limitation by glucose-6-phosphate dehydrogenase.
Oxidative stress is implicated in the pathogenesis of neurodegenerative disorders and brain ischemia, and hydrogen peroxide (H(2)O(2)) plays a central role in the stress. In this study, we have examined the kinetics of H(2)O(2) elimination by PC12 cells as a neuronal model in connection with the enzyme activities supporting the reaction. Similarly to other cell lines previously studied, H(2)O(2) removal kinetics could be divided into two reactions: one apparently following the Michaelis-Menten kinetics (GSH-dependent reaction) and the other following the first-order kinetics (mainly catalyzed by catalase). Based on the enzyme activities in the cell homogenate, it was inferred that glucose-6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme in the GSH- and NADPH-dependent H(2)O(2) elimination by PC12 cells. This is in contrast with fibroblasts and endothelial cells previously examined, in which glutathione reductase (GR) is rate-limiting in the reaction sequence. Treatment of PC12 cells with nerve growth factor increased G6PD activity in the cell homogenate and H(2)O(2) removal activity of the whole cells, with a concomitant increase in the resistance against H(2)O(2) toxicity. These results suggest the importance of G6PD in the antioxidant function of brain and pathogenesis of the oxidative stress-related diseases.
Center for Humanities and Sciences, Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394, Japan.
Kanae
K
Hashida
Yuki
Y
Sakakura
Nobuo
N
Makino
D000818:Animals; D002374:Catalase / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005954:Glucosephosphate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D007700:Kinetics; D016716:PC12 Cells / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D051381:Rats
D006861:Hydrogen Peroxide; D005954:Glucosephosphate Dehydrogenase; D002374:Catalase; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase