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Çiğdem A, Güller U. Purification and characterization of catechol oxidase from Posof Badele apple ( Malus domestica L): in vitro and in silico studies. INTERNATIONAL JOURNAL OF FOOD ENGINEERING 2022. [DOI: 10.1515/ijfe-2022-0022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
In the current study, polyphenol oxidase (PPO), responsible for enzymatic browning in fruits, was purified from Posof Badele apple (PB) (Malus domestica L.) in two steps as acetone precipitation and affinity chromatography. After purification, the purity of PBPPO was checked by using SDS-PAGE. It was figured out that PBPPO had maximum activity at pH 6.0 and 10 °C and it was stable at pH 5.5 and temperatures of 0–30 °C. Besides, it was determined that Al3+ and Cu2+ metal ions activated the enzyme and the PBPPO was strongly inhibited by ascorbic acid with a Ki constant of 1.67 ± 0.35 µM. Inhibitor-enzyme interactions were examined by molecular docking studies and it was revealed that ascorbic acid had the lowest docking score of −6.54 kcal/mol. We wanted to draw attention to the PB apple, which is red inside as well as outside and very rich in terms of nutrient content.
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Affiliation(s)
- Ayhan Çiğdem
- Department of Food Engineering , Faculty of Engineering, Iğdır University , Iğdır , Turkey
| | - Uğur Güller
- Department of Food Engineering , Faculty of Engineering, Iğdır University , Iğdır , Turkey
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Amperometric biosensors in an uncompetitive inhibition processes: a complete theoretical and numerical analysis. REACTION KINETICS MECHANISMS AND CATALYSIS 2021. [DOI: 10.1007/s11144-021-02015-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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3
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Arora S, Goraya RK, Siddiqui S, Gehlot R. Influence of anti‐browning treatments on enzymatic browning, distinctive properties, and microbiological characteristics of banana pulp during short‐term frozen storage. J FOOD PROCESS PRES 2021. [DOI: 10.1111/jfpp.15259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Simran Arora
- Food Grains and Oilseeds processing ICAR‐Central Institute of Post‐Harvest Engineering & Technology (CIPHET) Ludhiana India
| | | | - Saleem Siddiqui
- Centre of Food Science and Technology CCS Haryana Agricultural University Hisar India
| | - Rakesh Gehlot
- Centre of Food Science and Technology CCS Haryana Agricultural University Hisar India
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Kundu BK, Ranjan R, Mukherjee A, Mobin SM, Mukhopadhyay S. Mannich base Cu(II) complexes as biomimetic oxidative catalyst. J Inorg Biochem 2019; 195:164-173. [PMID: 30954693 DOI: 10.1016/j.jinorgbio.2019.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/23/2019] [Accepted: 03/28/2019] [Indexed: 11/16/2022]
Abstract
Galactose Oxidase (GOase) and catechol oxidase (COase) are the metalloenzymes of copper having monomeric and dimeric sites of coordination, respectively. This paper summarizes the results of our studies on the structural, spectral and catalytic properties of new mononuclear copper (II) complexes [CuL(OAc)] (1), and [CuL2] (2), (HL = 2,4‑dichloro‑6‑{[(2'‑dimethyl‑aminoethyl)methylamino]methyl}‑phenol) which can mimic the functionalities of the metalloenzymes GOase and COase. The structure of the compounds has been elucidated by X-ray crystallography and the mimicked Cu(II) catalysts were further characterized by EPR. These mimicked models were used for GOase and COase catalysis. The GOase catalytic results were identified by GC-MS and, analyzed by HPLC at room temperature. The conversion of benzyl alcohol to benzaldehyde were significant in presence of a strong base, Bu4NOMe in comparison to the neutral medium. Apart from that, despite of being monomeric in nature, both the homogeneous catalysts are very prone to participate in COase mimicking oxidation reaction. Nevertheless, during COase catalysis, complex 1 was found to convert 3,5‑ditertarybutyl catechol (3,5-DTBC) to 3,5‑ditertarybutyl quinone (3,5-DTBQ) having greater rate constant, kcat or turn over number (TON) value over complex 2. The generation of reactive intermediates during COase catalysis were accounted by electrospray ionization mass spectrometry (ESI-MS). Through mechanistic approach, we found that H2O2 is the byproduct for both the GOase and COase catalysis, thus, confirming the generation of reactive oxygen species during catalysis. Notably, complex 1 having mono-ligand coordinating atmosphere has superior catalytic activity for both cases in comparison to complex 2, that is having di-ligand environment.
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Affiliation(s)
- Bidyut Kumar Kundu
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | - Rishi Ranjan
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | | | - Shaikh M Mobin
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India
| | - Suman Mukhopadhyay
- Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India; Discipline of Biosciences and Biomedical Engineering, School of Engineering, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 453552, India.
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Mertens N, Mai F, Glomb MA. Influence of Nucleophilic Amino Acids on Enzymatic Browning Systems. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:1719-1725. [PMID: 30701971 DOI: 10.1021/acs.jafc.8b06458] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In the present study the enzymatic oxidation of gallic acid and catechin catalyzed by nashi pear polyphenol oxidase (PPO) in the presence of the amino acids lysine, arginine, or cysteine was investigated for polyphenol-amino acid adducts. HPLC analyses revealed the formation of two novel dihydrobenzothiazine carboxylic acid derivatives (8-(3',4'-dihydro-2 H-chromene-3',5',7'-triol)-3,4-dihydro-5-hydroxy-2 H-benzothiazine-3-carboxylic acid and 7-(3',4'-dihydro-2 H-chromene-3',5',7'-triol)-3,4-dihydro-5-hydroxy-2 H-benzothiazine-3-carboxylic acid) from 2'-cysteinyl catechin and 5'-cysteinyl catechin in cysteine incubations, respectively. In contrast, arginine and lysine did not lead to any amino acid adducts. Target compounds were separated by high-performance countercurrent chromatography and preparative HPLC and unequivocally characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. Mechanistic incubations starting from the catechin-cysteine adducts showed that both catechin and PPO are crucial components in the formation of the dihydrobenzothiazines. The cysteine incubations showed a red-brown coloration, which coincided with formation and degradation of the dihydrobenzothiazines finally leading to the formation of high-polymeric melanins. Therefore, these compounds might be the key intermediates to understand development of color during cysteine-driven enzymatic browning reactions.
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Affiliation(s)
- Nils Mertens
- Institute of Chemistry, Food Chemistry , Martin-Luther-University Halle-Wittenberg , Kurt-Mothes-Strasse 2 , 06120 Halle/Saale , Germany
| | - Franziska Mai
- Institute of Chemistry, Food Chemistry , Martin-Luther-University Halle-Wittenberg , Kurt-Mothes-Strasse 2 , 06120 Halle/Saale , Germany
| | - Marcus A Glomb
- Institute of Chemistry, Food Chemistry , Martin-Luther-University Halle-Wittenberg , Kurt-Mothes-Strasse 2 , 06120 Halle/Saale , Germany
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Abstract
Translation of mitochondrial encoded mRNAs by mitochondrial ribosomes is thought to play a major role in regulating the expression of mitochondrial proteins. However, the structure and function of plant mitochondrial ribosomes remains poorly understood. To study mitochondrial ribosomes, it is necessary to separate them from plastidic and cytosolic ribosomes that are generally present at much higher concentrations. Here, a straight forward protocol for the preparation of fractions highly enriched in mitochondrial ribosomes from plant cells is described. The method begins with purification of mitochondria followed by mitochondrial lysis and ultracentrifugation of released ribosomes through sucrose cushions and gradients. Dark-grown Arabidopsis cells were used in this example because of the ease with which good yields of pure mitochondria can be obtained from them. However, the steps for isolation of ribosomes from mitochondria could be applied to mitochondria obtained from other sources. Proteomic analyses of resulting fractions have confirmed strong enrichment of mitochondrial ribosomal proteins.
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Khan AU, Wei Y, Ahmad A, Haq Khan ZU, Tahir K, Khan SU, Muhammad N, Khan FU, Yuan Q. Enzymatic browning reduction in white cabbage, potent antibacterial and antioxidant activities of biogenic silver nanoparticles. J Mol Liq 2016. [DOI: 10.1016/j.molliq.2015.12.019] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Photocatalytic, antimicrobial activities of biogenic silver nanoparticles and electrochemical degradation of water soluble dyes at glassy carbon/silver modified past electrode using buffer solution. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2016; 156:100-7. [DOI: 10.1016/j.jphotobiol.2016.01.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 01/29/2016] [Indexed: 11/22/2022]
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Xu H, Zhang X, Karangwa E. Inhibition effects of Maillard reaction products derived from l-cysteine and glucose on enzymatic browning catalyzed by mushroom tyrosinase and characterization of active compounds by partial least squares regression analysis. RSC Adv 2016. [DOI: 10.1039/c6ra15769f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Inhibition of tyrosinase activity by Maillard reaction products derived from cysteine and glucose (Cys-MRPs) was studied.
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Affiliation(s)
- Haining Xu
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- PR China
| | - Xiaoming Zhang
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- PR China
| | - Eric Karangwa
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- PR China
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Kuijpers TFM, Narváez-Cuenca CE, Vincken JP, Verloop AJW, van Berkel WJH, Gruppen H. Inhibition of enzymatic browning of chlorogenic acid by sulfur-containing compounds. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2012; 60:3507-14. [PMID: 22416853 DOI: 10.1021/jf205290w] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The antibrowning activity of sodium hydrogen sulfite (NaHSO(3)) was compared to that of other sulfur-containing compounds. Inhibition of enzymatic browning was investigated using a model browning system consisting of mushroom tyrosinase and chlorogenic acid (5-CQA). Development of brown color (spectral analysis), oxygen consumption, and reaction product formation (RP-UHPLC-PDA-MS) were monitored in time. It was found that the compounds showing antibrowning activity either prevented browning by forming colorless addition products with o-quinones of 5-CQA (NaHSO(3), cysteine, and glutathione) or inhibiting the enzymatic activity of tyrosinase (NaHSO(3) and dithiothreitol). NaHSO(3) was different from the other sulfur-containing compounds investigated, because it showed a dual inhibitory effect on browning. Initial browning was prevented by trapping the o-quinones formed in colorless addition products (sulfochlorogenic acid), while at the same time, tyrosinase activity was inhibited in a time-dependent way, as shown by pre-incubation experiments of tyrosinase with NaHSO(3). Furthermore, it was demonstrated that sulfochlorogenic and cysteinylchlorogenic acids were not inhibitors of mushroom tyrosinase.
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Affiliation(s)
- Tomas F M Kuijpers
- Laboratory of Food Chemistry, Wageningen University, Wageningen, The Netherlands
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López-Nicolás JM, Pérez-López AJ, Carbonell-Barrachina A, García-Carmona F. Kinetic study of the activation of banana juice enzymatic browning by the addition of maltosyl-beta-cyclodextrin. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2007; 55:9655-9662. [PMID: 17929887 DOI: 10.1021/jf0713399] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In recent years, the use of cyclodextrins (CDs) as antibrowning agents in fruit juices has received growning attention. However, there has been no detailed study of the behavior of these molecules as substances, which can lead to the darkening of foods. In this paper, when the color of fresh banana juice was evaluated in the presence of different CDs, the evolution of several color parameters was the opposite of that observed in other fruit juices. Moreover, a kinetic model based on the complexation by CDs of the natural browning inhibitors present in banana is developed for the first time to clarify the enzymatic browning activation of banana juice. Finally, the apparent complexation constant between the natural polyphenoloxidase inhibitors present in banana juice and maltosyl-beta-CD was calculated (Kci = 27.026 +/- 0.212 mM (-1)).
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Affiliation(s)
- José M López-Nicolás
- Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus de Espinardo, 30071 Murcia, Spain.
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López-Nicolas JM, García-Carmona F. Use of cyclodextrins as secondary antioxidants to improve the color of fresh pear juice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2007; 55:6330-8. [PMID: 17608499 DOI: 10.1021/jf070819x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
In this paper, the color of fresh pear juice was evaluated for the first time in the presence of some natural and modified cyclodextrins (CDs) and the effect of these compounds as browning inhibitors was determined using the color space CIELAB system. Furthermore, because contradictory claims have been published concerning the mechanism by which enzymatic browning is inhibited by CDs, a kinetic model in the presence of CDs is proposed and the corresponding apparent complexation constants between the mixtures of diphenols present in pear juice and alpha-, beta-, and maltosyl-beta-CD have been calculated. Moreover, pear juice color was studied in the presence of different polyphenoloxidase inhibitors. Finally, we show that maltosyl-beta-CD enhances the ability of ascorbic acid to prevent enzymatic browning because of the protection that maltosyl-beta-CD offers against ascorbic acid oxidation. In this respect, maltosyl-beta-CD seems to act as a "secondary antioxidant", reducing pear juice browning and enhancing the naturally occurring antioxidant capacity of pear juice.
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Affiliation(s)
- José M López-Nicolas
- Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus de Espinardo, 30100, Murcia, Spain
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López-Nicolas JM, Pérez-López AJ, Carbonell-Barrachina A, García-Carmona F. Use of natural and modified cyclodextrins as inhibiting agents of peach juice enzymatic browning. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2007; 55:5312-9. [PMID: 17542611 DOI: 10.1021/jf070499h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
UNLABELLED Although cyclodextrins (CDs) have been successfully used as antibrowning agents in different fruit juices, no research has studied the effect of these compounds on enzymatic browning in peach juice. In this paper, the color of fresh peach juice was evaluated in the presence of two types of natural (alpha-CD and beta-CD) and a modified (maltosyl-beta-CD) CD, and the effectiveness of these compounds as browning inhibitors was determined using the color space CIELAB system. Moreover, to clarify the mechanism by which CDs inhibit peach juice enzymatic browning, the process was kinetically modeled in the absence and presence of CDs using a colorimetric method; the apparent complexation constants between the mixtures of diphenols present in peach juice and some types of CD were calculated. The results show that the highest affinity constant was presented by alpha-CD (Kc = 18.31 mM-1) followed by maltosyl-beta-CD (Kc = 11.17 mM-1), whereas beta-CD was incapable of inhibiting peach juice enzymatic browning. KEYWORDS Cyclodextrin; browning; peach; juice; color; polyphenol oxidase.
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Affiliation(s)
- José M López-Nicolas
- Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus de Espinardo, 30071 Murcia, Spain.
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García-Molina F, Peñalver MJ, Rodríguez-López JN, García-Cánovas F, Tudela J. Enzymatic method with polyphenol oxidase for the determination of cysteine and N-acetylcysteine. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2005; 53:6183-9. [PMID: 16076091 DOI: 10.1021/jf050197k] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Thiols, such as cysteine and N-acetylcysteine, are included in many pharmaceutical products for their mucolytic properties. The method described here uses mushroom polyphenol oxidase (PPO) to determine two thiols and consists of measuring the lag period in the formation of the product generated as PPO acts on o-diphenol in the presence of a thiol. In the experimental conditions, o-quinone is formed enzymatically and then reacts stoichiometrically with the thiol, originating the corresponding thiol-diphenol adduct, which does not absorb visible light. Once the thiol has been used up, the o-quinone can be observed in the medium. It must be borne in mind that the inhibition of PPO is practically null at low concentrations of thiol, and the only effect observed is the formation of the thiol-diphenol adduct. In the following, an exact kinetic method capable of rapidly and accurately assaying thiols with PPO and o-diphenol is optimized and is shown to be a straightforward way of calculating thiol concentration. The method has been successfully applied to the determination of cysteine in model solutions and of N-acetylcysteine in pharmaceutical products.
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Affiliation(s)
- F García-Molina
- Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain
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Valero E, Varón R, García-Carmona F. Catalytic oxidation of acetaminophen by tyrosinase in the presence of L-proline: a kinetic study. Arch Biochem Biophys 2003; 416:218-26. [PMID: 12893300 DOI: 10.1016/s0003-9861(03)00288-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A kinetic study of acetaminophen oxidation by tyrosinase in the presence of a physiological nucleophilic agent such as the amino acid L-proline is performed in the present paper. The o-quinone product of the catalytic activity, 4-acetamido-o-benzoquinone, becomes unstable through the chemical addition of L-proline, in competition with the nucleophilic addition of hydroxide ion from water. In both cases, the catechol intermediate, 3(')-hydroxyacetaminophen, is generated, as can be demonstrated by liquid chromatography. When the effect of the presence of the nucleophilic agent on the time course of the enzymatic reaction was kinetically analyzed, it was seen to decrease the duration of the lag period and increase the steady-state rate. Rate constants for the reaction of 4-acetamido-o-benzoquinone with water and L-proline were also determined. The results obtained in this paper open a new possibility to acetaminophen toxicity, that has been attributed hitherto to its corresponding p-quinone, N-acetyl-p-benzoquinone imine.
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Affiliation(s)
- Edelmira Valero
- GMB: Grupo de Modelización en Bioquímica, Departamento de Química-Física, Escuela Politécnica Superior de Albacete, Universidad de Castilla-La Mancha, Campus Universitario, Albacete E-02071, Spain.
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Inhibitory effect of unheated and heated d-glucose, d-fructose and l-cysteine solutions and Maillard reaction product model systems on polyphenoloxidase from apple. I. Enzymatic browning and enzyme activity inhibition using spectrophotometric and polarographic methods. Food Chem 2003. [DOI: 10.1016/s0308-8146(02)00376-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pruidze G, Mchedlishvili N, Omiadze N, Gulua L, Pruidze N. Multiple forms of phenol oxidase from Kolkhida tea leaves (Camelia Sinensis L.) and Mycelia Sterilia IBR 35219/2 and their role in tea production. Food Res Int 2003. [DOI: 10.1016/s0963-9969(03)00006-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Rodríguez-López JN, Fenoll LG, Peñalver MJ, García-Ruiz PA, Varón R, Martínez-Ortíz F, García-Cánovas F, Tudela J. Tyrosinase action on monophenols: evidence for direct enzymatic release of o-diphenol. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1548:238-56. [PMID: 11513969 DOI: 10.1016/s0167-4838(01)00237-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Using gas chromatography-mass spectrometry, the direct enzymatic release of o-diphenol (4-tert-butylcatechol) during the action of tyrosinase on a monophenol (4-tert-butylphenol) has been demonstrated for the first time in the literature. The findings confirm the previously proposed mechanism to explain the action of tyrosinase on monophenols (J.N. Rodríguez-López, J. Tudela, R. Varón, F. García-Carmona, F. García-Cánovas, J. Biol. Chem. 267 (1992)). Oxytyrosinase, the oxidized form of the enzyme with a peroxide group, is the only form capable of catalysing the transformation of monophenols into diphenols, giving rise to an enzyme-substrate complex in the process. The o-diphenol formed is then released from the enzyme-substrate complex or oxidized to the corresponding o-quinone. In order to detect the enzymatic release of o-diphenol, the non-enzymatic evolution of the o-quinone to generate o-diphenol by weak nucleophilic attack reactions and subsequent oxidation-reduction was blocked by the nucleophilic attack of an excess of cysteine. Furthermore, the addition of catalytic quantities of an auxiliary o-diphenol (e.g. catechol) considerably increases the accumulation of 4-tert-butylcatechol. The enzyme acting on 4-tert-butylphenol generates the enzyme-4-tert-butylcatechol complex and 4-tert-butylcatechol is then released (with k(-2)) generating mettyrosinase. The auxiliary o-diphenol added (catechol) and the 4-tert-butylcatechol generated by the enzyme then enter into competition. When [catechol] >> [4-tert-butylcatechol], the enzyme preferentially binds with the catechol to close the catalytic cycle, while 4-tert-butylcatechol is accumulated in the medium. In conclusion, we demonstrate that the enzyme produces 4-tert-butylcatechol from 4-tert-butylphenol, the concentration of which increases considerably in the presence of an auxiliary o-diphenol such as catechol.
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Affiliation(s)
- J N Rodríguez-López
- Grupo Investigación Enzimologia, Departmento de Bioquímica y Biologia Molecular-A, Facultad de Biologia, Univesidad de Murcia, Spain
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Navarro-Lozano MJ, Valero E, Varon R, Garcia-Carmona F. Kinetic study of an enzyme-catalysed reaction in the presence of novel irreversible-type inhibitors that react with the product of enzymatic catalysis. Bull Math Biol 1995; 57:157-68. [PMID: 7833851 DOI: 10.1007/bf02458321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In the present paper a kinetic study is made of the behaviour of a Michaelis-Menten enzyme-catalysed reaction in the presence of irreversible inhibitors rendered unstable in the medium by their reaction with the product of enzymatic catalysis. A general mechanism involving competitive, non-competitive, uncompetitive and mixed irreversible inhibition with one or two steps has been analysed. The differential equation that describes the kinetics of the reaction is non-linear and computer simulations of its dynamic behaviour are presented. The results obtained show that the systems studied here present kinetic co-operativity for a target enzyme that follows the simple Michaelis-Menten mechanism in its action on the substrate, except in the case of an uncompetitive-type inhibitor.
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Affiliation(s)
- M J Navarro-Lozano
- Departmento de Química-Física, Escuela Universitaria Politécnica de Albacete, Universidad de Castilla-La Mancha, Spain
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Nicolas JJ, Richard-Forget FC, Goupy PM, Amiot MJ, Aubert SY. Enzymatic browning reactions in apple and apple products. Crit Rev Food Sci Nutr 1994; 34:109-57. [PMID: 8011143 DOI: 10.1080/10408399409527653] [Citation(s) in RCA: 318] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This review examines the parameters of enzymatic browning in apple and apple products that is, phenolic compounds, polyphenoloxidases, and other factors (ascorbic acid and peroxidases), both qualitatively and quantitatively. Then the relationships between intensity of browning and the browning parameters are discussed, including a paragraph on the methods used for browning evaluation. Finally, the different methods for the control of browning are presented.
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Affiliation(s)
- J J Nicolas
- Chaire de Biochimie Industrielle et Agro-Alimentaire, Conservatoire National des Arts et Métiers, Paris, France
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