title: The contribution of stored malate and citrate to the substrate requirements of metabolism of ripening peach (Prunus persica L. Batsch) flesh is negligible. Implications for the occurrence of phosphoenolpyruvate carboxykinase and gluconeogenesis.
abstract: The first aim of this study was to determine the contribution of stored malate and citrate to the substrate requirements of metabolism in the ripening flesh of the peach (Prunus persica L. Batsch) cultivar Adriatica. In the flesh, stored malate accumulated before ripening could contribute little or nothing to the net substrate requirements of metabolism. This was because there was synthesis and not dissimilation of malate throughout ripening. Stored citrate could potentially contribute a very small amount (about 5.8%) of the substrate required by metabolism when the whole ripening period was considered, and a maximum of about 7.5% over the latter part of ripening. The second aim of this study was to investigate why phosphoenolpyruvate carboxykinase (PEPCK) an enzyme utilised in gluconeogenesis from malate and citrate is present in peach flesh. The occurrence and localisation of enzymes utilised in the metabolism of malate, citrate and amino acids were determined in peach flesh throughout its development. Phosphoenolpyruvate carboxylase (essential for the synthesis of malate and citrate) was present in the same cells and at the same time as PEPCK and NADP-malic enzyme (both utilised in the dissimilation of malate and citrate). A hypothesis is presented to explain the presence of these enzymes and to account for the likely occurrence of gluconeogenesis.
authors: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Via Borgo XX Giugno 74, 06121, Perugia, Italy. Electronic address: franco.famiani@unipg.it.
authors: Franco
authors: F
authors: Famiani
authors: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Via Borgo XX Giugno 74, 06121, Perugia, Italy.
authors: Daniela
authors: D
authors: Farinelli
authors: Istituto di Biologia Agroambientale e Forestale, CNR, Porano, TR, Italy.
authors: Stefano
authors: S
authors: Moscatello
authors: Istituto di Biologia Agroambientale e Forestale, CNR, Porano, TR, Italy.
authors: Alberto
authors: A
authors: Battistelli
authors: Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2 TN, UK.
authors: Richard C
authors: RC
authors: Leegood
authors: Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Via Borgo XX Giugno 74, 06121, Perugia, Italy. Electronic address: rob.walker@talktalk.net.
authors: Robert P
authors: RP
authors: Walker
mesh_terms: D019343:Citric Acid / Q000378:metabolism*; D005638:Fruit / Q000378:metabolism*; D005943:Gluconeogenesis / Q000502:physiology*; D008293:Malates / Q000378:metabolism*; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D000068239:Prunus persica / Q000378:metabolism*
chemical_list: D008293:Malates; D010940:Plant Proteins; D019343:Citric Acid; C030298:malic acid; D019764:Phosphoenolpyruvate Carboxykinase (ATP)
keywords: Ammonium; Citrate; Gluconeogenesis; Malate; Peach; Phosphoenolpyruvate carboxykinase; Ripening