Polyphenol oxidase activity

Zakharova and co-workers studied a red variety in 1997 to gain a closer insight into its polyphenol oxidase activity. More recently, a study addressing the antioxidant properties of a red colored Swiss chard was published. However, the pigments were erroneously addressed as anthocyanins. 

Martyn RD, Samuelson DA, Freeman TB. Ultrastructural localization of polyphenol oxidase activity in leaves of healthy and disease water hyacinth. Phytopathology 1979 69 1278-1287. 

Because yams are stored in open systems at ambient temperatures (usually warm), tuber tissue was examined for proteinase activity at 40°C. Some tubers had high apparent polyphenol oxidase activity upon peeling of the tubers (tissue turned deep purple at the peeled surface) so that PYP was added to extracts to combine with polyphenolic compounds and protect the proteinase from reacting with these compounds. Earlier studies had shown some inhibition of alkaline proteinase activity by ferric ion (24) so that EDTA was also added to the extracts to chelate any free iron. Two alkaline pH optima were found, at 9.0 and 10.5. The alkaline proteinases of white potatoes (Solanum tuberosum) have pH optima between 8.6 and 9 (25) and those of Carilla chocola tubers have pH optima between 8.0 and 9.5 (26,27T, suggesting that alkaline... 

Figure 4. Changes in polyphenol oxidase activity (-0-) and phenolic compounds (0) in Chinese cabbage tissue after injury by Luygus disponsi (29).

Polyphenol oxidase (PPO) (EC 1.14.18.1 monophenol monooxygenase [tyrosinase] or EC 1.10.3.2 0-diphenol 02-oxidoreductase) is one of the more important enzymes involved in the formation of black tea polyphenols. The enzyme is a metallo-protein thought to contain a binudear copper active site. The substance PPO is an oligomeric particulate protein thought to be bound to the plant membranes. The bound form of the enzyme is latent and activation is likely to be dependent upon solubilization of the protein (35). PPO is distributed throughout the plant (35) and is localized within in the mitochondria (36), the cholorplasts (37), and the peroxisomes (38). Using antibody techniques, polyphenol oxidase activity has also been localized in the epidermis palisade cells (39). Reviews on the subject of PPO are available (40—42). 

In the authors experience, the pigments of a wide variety of plant materials have been stable in the aqueous acetone extract. However, problems have been encountered with pigment degradation for certain potato cultivars with high polyphenol oxidase activity. This problem can be circumvented by putting the aqueous acetone extract (uncapped) in a boiling water bath for 5 min. After heating, the volume of acetone lost by evaporation should be replenished. This enzyme inactivation step has been found unnecessary for most materials. 

Polyphenol Oxidases. Plant trichomes and their exudates confer resistance to a variety of insects (54-56). In solanaceous plants, such as the tomato and potato, trichomes contain polyphenol oxidases and catecholic phenolics (e.g., caffeic and chlorogenic acids), which contribute to resistance to a variety of insect pests. In the potato plant, the polyphenol oxidases and phenolics are separated in different trichomes. When insects, such as aphids or leaf hoppers, walk across the surface of the plant they break the two types of trichomes. Trichomal fluids are liberated and, upon mixing, polymerize as a result of polyphenol oxidase activity on catechols, forming an often lethal adhesive trap for the insects (52,58) In tomato plants, the polyphenol oxidase and chlorogenic acid are separated by intracellular compartments, but upon breakage of trichomes by insects, polymerization and physical entrapment occurs (54). 

Table V. The Effect of Tomato Plant Foliar Polyphenol Oxidase Activity on Proteinase Inhibitors in Snodoptera exigua...

BRs do not affect the peroxidase and polyphenol oxidase activities (this is in contrast with auxin action), a fact indicating the synthesis of specific proteins by BRs. 

Heimdal H, Bro R, Larsen LM, Poll L, Prediction of polyphenol oxidase activity in model solutions containing various combinations of chlorogenic acid, (—)-epicatechin, 02, C02, temperature and pH by multiway analysis, Journal of Agricultural and Food Chemistry, 1997, 45, 2399-2406. 

Polyphenol Oxidase Activity and Enzymatic Browning in Mushrooms... 

In between the lines of haptoglobin and a2-macroglobulin, the light line caused by ceruloplasmin is just visible (U2). It is the principal carrier of copper, 8 atoms per molecule besides, it contains 9.5 % of hexoses and has a molecular weight of 150,000 (S9). Its polyphenol-oxidase activity can be used for localization and, coupled with ImEl, for identification. 

Munshi, C. B., and Mondy, N. I. (1988). Effect of soil applications of sodium molybdate on the quality of potatoes polyphenol oxidase activity, enzymatic discoloration, phenol and ascorbic acid. J. Agric. Food Chem. 36 919-22. 

In hybrid poplar and trembling aspen, leaf damage by wounding or herbivory induces polyphenol oxidase activity (PPO EC 1.10.3.2). This enzyme can... 

When polyphenol oxidase activity was controlled, phospholipase activities ranged from 1.04 to 11.60 J mol/min/gfw in the leaves of 41 North American cultivars (6). These values are much higher than those previously reported for potato leaves (.009 pmol/min/gfw)... 

Bayindirli et al. (2006) studied the effectiveness of treating polyphenol oxidase activity in apple juice by applying high hydrostatic pressure with mild heat treatment (350 MPa at 40 °Q. 

Hatcher, D.W. and Kruger, J.E., Simple phenolic acids in flours prepared from Canadian wheat Relationship to ash content, color, and polyphenol oxidase activity. Cereal Chem., 74, 337, 1997. 

Almeida, M.E. and Nogueira, J.N. The control of polyphenol oxidase activity in fruits and vegetables—A study of the interactions between the chemical compounds used and heat treatment, Plant Foods Hum. Nutr., 43, 245, 1995. 

Ma, S.X. et al. Prevention of enzymatic darkening in frozen sweet potatoes [Ipomoea batatas (L.) Lam.] by water blanching Relationship among darkening, phenols, and polyphenol oxidase activity, J. Aerie. Food Chem., 40, 864, 1992. 

Devece, C. et al. Enzyme inactivation analysis for indushial blanching appheations Comparison of microwave, conventional, and combination heat treatments on mushroom polyphenol oxidase activity, J. Agric. Food Chem., 47, 4506, 1999. 

Ballestra, P. et al. Effect of high-pressure treatment on polyphenol oxidase activity of the Agaricus bispo-rus mushroom. High Press. Res., 22, 677, 2002. 

Gui, F. et al. Change of polyphenol oxidase activity, color, and browning degree during storage of cloudy apple juice treated by supercritical carbon dioxide, Eur. Food Res. Technol., 223, 427, 2006. 

Rocha, A.M.C.N. and Morals, A.M.M.B. Polyphenol oxidase activity of minimally processed Jonagord apples (Malus domestica), J. Food Process. Preserv., 29, 8, 2005. 

Browning and hardening of exudate on the insect s mouthparts and tarsi is due to the enzymatic activity of an O2- requiring oxidase (12), and has been associated with both peroxidase and polyphenol oxidase activities (2/14-fl2.). We recently showed that these enzymatic activities are due to a 59 kD polyphenol oxidase (PPO) which is present in the type A trichomes of S. berthaultii at approximately 1 ng/trichome head (a concentration of approximately 0.3 mM) (lA). The specialization of the glandular trichome is reflected in the fact that PPO comprises approximately 60% of the total soluble protein of the organ. 

Raj, S.N., Sarosh, B.R., and Shetty, H.S. 2006. Induction and accumulation of polyphenol oxidase activities as implicated in development of resistance against pearl millet downy mildew diseases. Fund. Plant Biol., 33 563-571. 

Chang S, Tan C, Frankel EN, Barrett DM (2000) Low-density lipoprotein antioxidant activity of phenolic compounds and polyphenol oxidase activity in selected clingstone peach cultivars. J Agric Food Chem 48 147-151... 

Latham MJ, Storry JE, Sharpe ME (1972) Effect of low-roughage diets on the microflora and lipid metabolism in the rumen. Appl Environ Microbiol 24 871-877 Lee MRF, Winters AL, ScoUan ND, Dewhurst RJ, Theodorou MK, Minchin FR (2004) Plant mediated lipolysis and proteolysis in red clover with different polyphenol oxidase activities. J Sd Food Agric 84 1639-1645... 

Lee MRF, Parfitt LJ, ScoUan ND, Minchin FR (2007) Lipolysis in red clover with different polyphenol oxidase activities in the presence and absence of rumen fluid. J Sci Food Agric 87 1208-1314... 

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