Partial purification and characterization of polyphenol oxidase from artichoke (Cynara scolymus L.) heads

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dc.contributor.authorAydemir T.
dc.date.accessioned2024-07-22T08:24:15Z
dc.date.available2024-07-22T08:24:15Z
dc.date.issued2004
dc.description.abstractPartial characterization of polyphenol oxidase activity in artichoke heads is described. Stable and highly active PPO extracts were obtained using 1.0% (w/v) polyethylene glycol (PEG), 1.5% (w/v) Triton X-100 and 0.1% NaCl in 0.2 M potassium phosphate buffer, pH 6.0. Three isoenzymes of the artichoke PPO were detected by polyacrylamide gel electrophoresis. The pH optimum for artichoke PPO was found to be a very broad (5.0-7.0) and the enzyme activity was stable in the range 6.0-7.0 at 25°C for 60 min. The optimum temperature was 25°C. The enzyme was heat-stable between 20 and 30°C and completely inactivated at 80°C after 5 min. The activation energy (Ea) with catechol was 15.8 kJ/mol at pH 6.0. PPO showed activity to catechol, pyrogallol and 4-methylcatechol, DL-dopa, L-dopa and gallic acid. (Km and V max values were 10.2 mM and 19,662 U/ml min for catechol, 12.4 mM and 12,500 U/ml min for 4-methylcatechol, 14.3 mM and 8065 U/ml min for pyrogallol, 37.7 mM and 5865 U/ml min for L-dopa 36.3 mM and 6060 U/ml min for DL-dopa, 43.6 mM and 4620 U/ml min for gallic acid, respectively). L-tyrosine was also tested but was not oxidized by artichoke PPO. The I50 values of inhibitors studied on PPO were determined by means of activity percentage (I50) diagrams. The values were 6.17×10-5 M, 6.32×10-5 M, 9.11×10-5 M, 1.76×10 -5 M, 1.47×10-5 M, 8.33×10-5 M, 4.12×10-5 M, 1.94×10-4 M and 1.83×10-5 M for glutathione, thiourea, sodium azide, sodium metabisulfite, dithiothreitol, β-mercaptoethanol, sodium diethyl dithiocarbamate, oxalic acid and ascorbic acid, respectively. Therefore, the most effective inhibitor was dithiothreitol, followed in decreasing order by sodium metabisulphide and ascorbic acid. Metal ions (Zn++, Ba ++, Cu++) were poor inhibitors of the enzyme at 10 mM. © 2003 Elsevier Ltd. All rights reserved.
dc.identifier.DOI-ID10.1016/j.foodchem.2003.10.017
dc.identifier.issn03088146
dc.identifier.urihttp://akademikarsiv.cbu.edu.tr:4000/handle/123456789/19878
dc.language.isoEnglish
dc.subjectCynara
dc.subjectCynara scolymus
dc.subjectScolymus
dc.subjectascorbic acid
dc.subjectbuffer
dc.subjectcatechol
dc.subjectcatechol oxidase
dc.subjectdiethyldithiocarbamic acid
dc.subjectdithiothreitol
dc.subjectDOPA
dc.subjectdopamine
dc.subjectgallic acid
dc.subjectglutathione
dc.subjectmacrogol
dc.subjectmercaptoethanol
dc.subjectmethyl group
dc.subjectoxalic acid
dc.subjectpotassium dihydrogen phosphate
dc.subjectpyrogallol
dc.subjectsodium azide
dc.subjectsodium metabisulfite
dc.subjectthiourea
dc.subjecttyrosine
dc.subjectacidity
dc.subjectalkalinity
dc.subjectartichoke
dc.subjectarticle
dc.subjectconcentration response
dc.subjectcontrolled study
dc.subjectenzyme activity
dc.subjectenzyme assay
dc.subjectenzyme inactivation
dc.subjectenzyme purification
dc.subjectenzyme stability
dc.subjectfood biotechnology
dc.subjectheating
dc.subjectnonhuman
dc.subjectoxidation
dc.subjectphytochemistry
dc.subjectpolyacrylamide gel electrophoresis
dc.subjecttemperature dependence
dc.titlePartial purification and characterization of polyphenol oxidase from artichoke (Cynara scolymus L.) heads
dc.typeArticle

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