title: Phosphoenolpyruvate metabolism in Jerusalem artichoke mitochondria.
abstract: We report here initial studies on phosphoenolpyruvate metabolism in coupled mitochondria isolated from Jerusalem artichoke tubers. It was found that: (1) phosphoenolpyruvate can be metabolized by Jerusalem artichoke mitochondria by virtue of the presence of the mitochondrial pyruvate kinase, shown both immunologically and functionally, located in the inner mitochondrial compartments and distinct from the cytosolic pyruvate kinase as shown by the different pH and inhibition profiles. (2) Jerusalem artichoke mitochondria can take up externally added phosphoenolpyruvate in a proton compensated manner, in a carrier-mediated process which was investigated by measuring fluorimetrically the oxidation of intramitochondrial pyridine nucleotide which occurs as a result of phosphoenolpyruvate uptake and alternative oxidase activation. (3) The addition of phosphoenolpyruvate causes pyruvate and ATP production, as monitored via HPLC, with their efflux into the extramitochondrial phase investigated fluorimetrically. Such an efflux occurs via the putative phosphoenolpyruvate/pyruvate and phosphoenolpyruvate/ATP antiporters, which differ from each other and from the pyruvate and the adenine nucleotide carriers, in the light of the different sensitivity to non-penetrant compounds. These carriers were shown to regulate the rate of efflux of both pyruvate and ATP. The appearance of citrate and oxaloacetate outside mitochondria was also found as a result of phosphoenolpyruvate addition.
authors.affiliation: Istituto di Biomembrane e Bioenergetica, CNR, Via G. Amendola 165/A, 70126, Bari, Italy.
authors.forename: Lidia
authors.initials: L
authors.lastname: de Bari
authors.forename: Daniela
authors.initials: D
authors.lastname: Valenti
authors.forename: Roberto
authors.initials: R
authors.lastname: Pizzuto
authors.forename: Anna
authors.initials: A
authors.lastname: Atlante
authors.forename: Salvatore
authors.initials: S
authors.lastname: Passarella
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D001692:Biological Transport; D006368:Helianthus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D010728:Phosphoenolpyruvate / Q000378:metabolism* / Q000494:pharmacology; D011770:Pyruvate Kinase / Q000032:analysis / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D010728:Phosphoenolpyruvate; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D011770:Pyruvate Kinase