title: Enzyme characterisation, isolation and cDNA cloning of polyphenol oxidase in the hearts of palm of three commercially important species.
abstract: Heart of palm (palmito) is the edible part of the apical meristem of palms and is considered a gourmet vegetable. Palmitos from the palms Euterpe edulis (Juçara) and Euterpe oleracea (Açaí) oxidise after harvesting, whereas almost no oxidation is observed in palmitos from Bactris gasipaes (Pupunha). Previous investigations showed that oxidation in Juçara and Açaí was mainly attributable to polyphenol oxidase (PPO; EC 1.14.18.1) activity. In this study, we partially purified PPOs from these three palmitos and analysed them for SDS activation, substrate specificity, inhibition by specific inhibitors, thermal stability, optimum pH and temperature conditions, Km and Ki. In addition, the total phenolic content and chlorogenic acid content were determined. Two partial cDNA sequences were isolated and sequenced from Açaí (EoPPO1) and Juçara (EePPO1). Semi-quantitative RT-PCR expression assays showed that Açaí and Juçara PPOs were strongly expressed in palmitos and weakly expressed in leaves. No amplification was observed for Pupunha samples. The lack of oxidation in the palmito Pupunha might be explained by the low PPO expression, low enzyme activity or the phenolic profile, particularly the low content of chlorogenic acid.
authors.affiliation: Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, CP 6109, 13083-970 Campinas, SP, Brazil.
authors.forename: Milton Massao
authors.initials: MM
authors.lastname: Shimizu
authors.forename: Geraldo Aclécio
authors.initials: GA
authors.lastname: Melo
authors.forename: Adriana
authors.initials: A
authors.lastname: Brombini Dos Santos
authors.forename: Alexandra
authors.initials: A
authors.lastname: Bottcher
authors.forename: Igor
authors.initials: I
authors.lastname: Cesarino
authors.forename: Pedro
authors.initials: P
authors.lastname: Araújo
authors.forename: Jullyana Cristina
authors.initials: JC
authors.lastname: Magalhães Silva Moura
authors.forename: Paulo
authors.initials: P
authors.lastname: Mazzafera
mesh_terms: D028023:Arecaceae / Q000201:enzymology / Q000235:genetics; D004156:Catechol Oxidase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000737:chemistry; D004795:Enzyme Stability / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D013379:Substrate Specificity / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D010940:Plant Proteins; D004156:Catechol Oxidase