title: Inhibition of mitochondrial respiration by phosphoenolpyruvate.
abstract: The cytosolic factors that influence mitochondrial oxidative phosphorylation rates are relatively unknown. In this report, we examine the effects of phosphoenolpyruvate (PEP), a glycolytic intermediate, on mitochondrial function. It is reported here that in rat heart mitochondria, PEP delays the onset of state 3 respiration in mitochondria supplied with either NADH-linked substrates or succinate. However, the maximal rate of state 3 respiration is only inhibited when oxidative phosphorylation is supported by NADH-linked substrates. The capacity of PEP to delay and/or inhibit state 3 respiration is dependent upon the presence or absence of ATP. Inhibition of state 3 is exacerbated in uncoupled mitochondria, with a 40% decrease in respiration seen with 0.1mM PEP. In contrast, ATP added exogenously or produced by oxidative phosphorylation completely prevents PEP-mediated inhibition. Mechanistically, the results support the conclusion that the main effects of PEP are to impede ADP uptake and inhibit NADH oxidation. By altering the NADH/NAD(+) status of mitochondria, it is demonstrated that PEP enhances succinate dehydrogenase activity and increase free radical production. The results of this study indicate PEP may be an important modulator of mitochondrial function under conditions of decreased ATP.
authors.affiliation: Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.
authors.forename: C Nathan
authors.initials: CN
authors.lastname: Baily
authors.forename: Roger W
authors.initials: RW
authors.lastname: Cason
authors.forename: Shraddha S
authors.initials: SS
authors.lastname: Vadvalkar
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsuzaki
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Humphries
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019069:Cell Respiration; D005609:Free Radicals / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D005609:Free Radicals; D009243:NAD; D010728:Phosphoenolpyruvate; D000255:Adenosine Triphosphate; D019802:Succinic Acid; D006861:Hydrogen Peroxide