Polyphenol oxidase
Polyphenol oxidase (PPO or monophenol monooxygenase) is a tetramer that contains four atoms of copper per molecule, and binding sites for two aromatic compounds and oxygen. The enzyme catalyses the o-hydroxylation of monophenols (phenol molecules in which the benzene ring contains a single hydroxyl substituent) to o-diphenols (phenol molecules containing two hydroxyl substituents). They can also further catalyse the oxidation of o-diphenols to produce o-quinones. It is the rapid polymerisation of o-quinones to produce black, brown or red pigments (polyphenols) that is the cause of fruit browning. The amino acid tyrosine contains a single phenolic ring that may be oxidised by the action of PPOs to form o-quinone. Hence, PPOs may also be referred to as tyrosinases.
Enzyme nomenclature differentiates between monophenol oxidase enzymes (tyrosinases) and o-diphenol:oxygen oxidoreductase enzymes (catechol oxidases). Therefore, please refer to the tyrosinase and catechol oxidase articles for more information on polyphenol oxidase enzymes.
A mixture of monophenol oxidase and catechol oxidase enzymes is present in nearly all plant tissues, and can also be found in bacteria, animals, and fungi. In insects, cuticular polyphenol oxidases are present and their products are responsible for desiccation tolerance.
In fact, browning by PPO is not always an undesirable reaction; the familiar brown color of tea and cocoa is developed by PPO enzymatic browning during product processing.
Tentoxin has also been used in recent research to eliminate the polyphenol oxidase activity from seedlings of higher plants.Tropolone is a grape polyphenol oxidase inhibitor. Another inhibitor of this enzyme is potassium pyrosulphite (K2S2O5).

This is an excerpt from the article Polyphenol oxidase from the Wikipedia free encyclopedia. A list of authors is available at Wikipedia.
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Polyphenol Oxidase Causes Browning of…
Polyphenol oxidase (PPO) enzymes, also known as polyphenoloxidases, are able to catalyze the transformation of an array of aromatic compounds that have two adjacent ...
TLC Cooking "Why do apples and potatoes…
Why do apples and potatoes turn brown when you slice them? How do you keep them from turning brown? Find out the answer in this article.
Polyphenol oxidase - Wikipedia, the free encyclopedia
Polyphenol oxidase (PPO or monophenol monooxygenase) is a tetramer that contains four atoms of copper per molecule, and binding sites for two aromatic ...
Polyphenol Oxidase - Worthington Enzyme Manual
Polyphenol oxidase (tyrosinase) (TY) is a bifunctional, copper-containing oxidase having both catecholase and cresolase activity (Malmström and Rydén 1968): ...
Polyphenol oxidases in plants and fungi: Going places? A review
The more recent reports on Polyphenol oxidase in plants and fungi are reviewed. ... tribution, location and properties of Polyphenol oxidase (PPO) as well as ...
Polyphenol Oxidase in Potato' - Plant Physiology
Polyphenol oxidase (PPO) activity in potato (Solanum tubero- sum) plants was high in stolons, tubers, roots, and flowers but low in leaves and stems.
Polyphenol oxidase - definition from Biology-Online.org
Definition and other additional information on Polyphenol oxidase from Biology- Online.org dictionary.
Polyphenol oxidase and peroxidase in fruits and vegetables.
Polyphenol oxidases and peroxidases are among the most studied enzymes in fruits and vegetables. Owing to the deleterious effects of discoloration and ...
Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta
POLYPHENOLOXIDASE IN BETA VULGARIS. Daniel I. Arnon* ... Localization of polyphenoloxidase in the chloroplasts of Beta vulgaris. Nature. 1948 Aug 28 ...
Enzymic browning in potatoes: A simple assay for a polyphenol ...
Enzymic browning in potatoes: a simple assay for a Polyphenol oxidase catalysed reaction. J.M. Busch*. Animal and Food Sciences Division, Lincoln University, ...
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[PDF]characterization of polyphenol oxidase and antioxidants from ...
Fang, Caodi, "CHARACTERIZATION OF Polyphenol oxidase AND ANTIOXIDANTS FROM PAWPAW (ASIMINA. TRIBOLA) FRUIT" (2007). University of ...
Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta
[PDF]Inhibition of Polyphenol Oxidase, Pectin Methylesterase
Monte Corporation throughout my study at Washington State University. Finally ... Polyphenol oxidase (PPO) catalyzes oxidation of phenolic compounds into o- ...
"Comparison of the content of phenolic compounds, polyphenol ...
Comparison of the content of phenolic compounds, Polyphenol oxidase and peroxidase in grains of fifty ... Willem J. H. van BERKEL, Wageningen University ...
Aberystwyth University - Winters, Dr Ana
My more recent work has focussed on the enzyme Polyphenol oxidase in forage crops looking ... Role of red clover Polyphenol oxidase in pathogen resistance ...
[PDF]Characterization of Polyphenol Oxidase in Sweet ... - UCSI University
Department of Biotechnology, Faculty of Applied Sciences, UCSI University, No. ... Polyphenol oxidases (PPOs) from several plant species, including sweet ...
Red clover polyphenol oxidase and lipid metabolism - University of ...
TY - JOUR. T1 - Red clover Polyphenol oxidase and lipid metabolism. A1 - Van Ranst,G. A1 - Lee,M. R. F.. A1 - Fievez,V. AU - Van Ranst,G. AU - Lee,M. R. F. ...
[PDF]Catalase, Peroxidase, and Polyphenoloxidase ... - Plant Physiology
Catalase activity decreased while peroxidase and polyphenoloxidase activi- ties increased during ... Department of Botany, Utkal University. 2 Present address: ...
[PDF]Inhibition of Apple Polyphenol Oxidase Activity by Sodium Chlorite
undertaken to investigate the inhibitory effect of SC on Polyphenol oxidase (PPO) and the associated mechanisms. ... University of Illinois at Urbana-Champaign.
[PDF]Peroxidase and Polyphenoloxidase Activities and Free Ninhydrin ...
DigitalCommons@University of Nebraska - Lincoln. Monson, W. G. and Haskins, Francis A., "Peroxidase and Polyphenoloxidase Activities and Free ...
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Polyphenol oxidase
Peroxidase and polyphenoloxidase activities in uvaia fruit at different maturation stages | WFL Publisher
Lab Determining the Degree of Specifity of the Enzymes Polyphenol Oxidase and Peroxidase
Title: Preparation and Assay of Phenolase and Peroxidase from Sweet and Irish Potato.
Construction of the Vector for Endosperm Specific Polyphenol Oxidase RNA Interference and Its Transformation in Common Wheat » Agricultural Science Paper
]]> Title Construction of the Vector for Endosperm Specific Polyphenol oxidase RNA Interference and Its Transformation in Common Wheat Abstract Polyphenol oxidase (PPO) is one of the primary factors in brown causing of the dough. Blocking or limiting the express of ppo genes is meaningful to enhance whiteness of flour product.
Study on Isolation and Immobilization of Polyphenol Oxidase | STMOPEN.net
Polyphenol oxidase was purified from leaves of Nicotiana tobaccum and the needle shape crystals were formed. The enzyme was immobilized on nylon membrane with glutaraldehyde as the cross linking agent.
Analysis of Polyphenoloxidase Enzyme Activity From Potato Extract
Analysis of Polyphenoloxidase Enzyme Activity from Potato Extract Biochemistry Lab I (CHEM 4401) Student Supplement Background (Bring your Practical Buffer Preparation Supplement to lab) Enzymes are protein molecules (primarily) that serve as biological catalysts.
How does blanching affect the enzyme polyphenol oxidase to stop the browning... - Question #302264 - Homework Help
Topic: Science. Question: How does blanching affect the enzyme Polyphenol oxidase to stop the browning... - Question #302264
The enzyme activity of Polyphenol oxidase (PPO) in grain is regarded as a major factor in time-dependent darkening and discoloration of wheat food products during processing or storage. The darkening phenomena of products reduce the quality of products and affect consumer acceptance. Breeding wheat cultivars with low PPO activity is the best way to reduce the undesirable darkening. The low PPO line PI 117635 was crossed to two low PPO wheats from Idaho, IDO580 and IDO377s to determine whether matings between wheats with low levels of grain PPO would result in complementation, and lines with lower or nil PPO would be generated. The F3:4 population derived from PI 117635/IDO580 showed no variation in PPO activity. The F3:5 and F3:6 populations derived from PI 117635/IDO377s grown at Yuma and Oregon fields in 2009 were analyzed for PPO activity and used to determine whether lines with nil PPO activity were generated. Of the 239 lines, 154 lines were identified to have PPO activity that was not significantly different from Ben durum wheat using t-test. STS markers, PPO18, PPO29, and STS01 were used to test lines possibly with either low or high PPO levels at Ppo-A1 and Ppo-D1 loci. All lines were fixed for the low PPO allele at Ppo-A1. However, PPO29 and STS01 showed the opposite results from the Ppo-D1 allele prediction. To examine inheritance of PPO activity in multiple wheat genetic backgrounds and to evaluate the relationship between PPO activity and alleles at two PPO loci, 5 populations (PI 117635/Antelope; Fielder/NE03681; Fielder/Antelope; NW07OR1070/Antelope; NW07OR1066/OR2050272H) were developed. STS markers were used to identify the genotypes and a putative third (null) genotype at Ppo-A1 allele was discovered in NW07OR1066 and NW07OR1070 lines. ANOVA showed all populations had significant genotypic effects on PPO activity. The generations and genotype nested within generation effects were not significant in all populations. The NW07OR1070/Antelope and NW07OR1066/OR2050272H populations had the lowest PPO activities because both populations had a null allele for Ppo-A1 on chromosome 2A. Of all 5 populations, 3 populations found the reverse results of Ppo-D1 allele from the previously reported research, indicating the markers for Ppo-D1 allele give erroneous results in some genetic backgrounds. Advisor: P. Stephen Baenziger
IJMS | Free Full-Text | Molecular Modeling of Peroxidase and Polyphenol Oxidase: Substrate Specificity and Active Site Comparison
International Journal of Molecular Sciences, an international, peer-reviewed Open Access journal.
"Wheat Polyphenol Oxidase: Distribution and Genetic Mapping in Three In" by Tigst Demeke, Craig F. Morris et al.
The enzyme Polyphenol oxidase (PPO) has been implicated in discoloration of Asian noodles. The recombinant inbred line (RIL) populations, M6/‘Opata 85’, NY18/CC, and ND2603/‘Butte 86’ were used to investigate the distribution, chromosome location, and number of loci involved in wheat (Triticum aestivum L.) PPO. PPO activity was measured by means of the substrates L-DOPA (L-3,4-dihydroxyphenyl-alanine) and L-tyrosine. The M6/Opata 85 RIL population had a normal distribution, while the ND2603/Butte 86 RIL population had a bimodal distribution for PPO activity (L-DOPA assay).
"Prediction of Polyphenol Oxidase Activity Using Visible Near-Infrared " by Edurne Gaston, Jesus Maria Frias et al.
Physical stress (i.e. bruising) during harvesting, handling and transportation triggers enzymatic discoloration of mushrooms, a common and detrimental phenomenon largely mediated by Polyphenol oxidase (PPO) enzymes. Hyperspectral imaging (HSI) is a non-destructive technique that combines imaging and spectroscopy to obtain information from a sample. The objective of this study was to assess the ability of HSI to predict the activity of PPO on mushroom caps. Hyperspectral images of mushrooms subjected to various damage treatments were taken, followed by enzyme extraction and PPO activity measurement. Principal component regression (PCR) models (each with 3 PCs) built on raw reflectance and multiple scatter corrected (MSC) reflectance data were found to be the best modeling approach. Prediction maps showed that the MSC model allowed for compensation of spectral differences due to sample curvature and surface irregularities. Results reveal the possibility of developing a sensor which could rapidly identify mushrooms with higher likelihood to develop enzymatic browning and hence aid produce management decision makers in the industry.