Physicochemical Properties and Function of Plant Polyphenol Oxidase: A Review

Yoruk, R.; Marshall, Maurice R.

doi:10.1111/j.1745-4514.2003.tb00289.x

Cited by 505 publications

(536 citation statements)

References 230 publications

(330 reference statements)

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“…When binding with other phenols, a melanin-like polyphenolic structure in and between proteins can be formed. This results in a brown colour, which is undesirable in fruit and vegetables (Yoruk and Marshall, 2003).…”

Section: Introductionmentioning

confidence: 99%

Red clover polyphenol oxidase and lipid metabolism

Ranst

Lee

Fievez

2011

Animal

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Increasing the polyunsaturated fatty acid (PUFA) composition of milk is acknowledged to be of benefit to consumer health. Despite the high PUFA content of forages, milk fat contains only about 3% of PUFA and only about 0.5% of n-3 fatty acids. This is mainly due to intensive lipid metabolism in the rumen (lipolysis and biohydrogenation) and during conservation (lipolysis and oxidation) such as drying (hay) and ensiling (silage). In red clover, polyphenol oxidase (PPO) has been suggested to protect lipids against degradation, both in the silage as well as in the rumen, leading to a higher output of PUFA in ruminant products (meat and milk). PPO mediates the oxidation of phenols and diphenols to quinones, which will readily react with nucleophilic binding sites. Such binding sites can be found on proteins, resulting in the formation of protein-bound phenols. This review summarizes the different methods that have been used to assess PPO activity in red clover, and an overview on the current understanding of PPO activity and activation in red clover. Knowledge on these aspects is of major importance to fully harness PPO's lipid-protecting role. Furthermore, we review the studies that evidence PPO-mediated lipid protection and discuss its possible importance in lab-scale silages and further in an in vitro rumen system. It is demonstrated that high (induction of) PPO activity can lead to lower lipolysis in the silage and lower biohydrogenation in the rumen. There are three hypotheses on its working mechanism: (i) protein-bound phenols could directly bind to enzymes (e.g. lipases) as such inhibiting them; (ii) binding of quinones in and between proteins embedded in a lipid membrane (e.g. in the chloroplast) could lead to encapsulation of the lipids; (iii) direct binding of quinones to nucleophilic sites in polar lipids also could lead to protection. There is no exclusive evidence on which mechanism is most important, although there are strong indications that only lipid encapsulation in protein-phenol complexes would lead to an effective protection of lipids against ruminal biohydrogenation. From several studies it has also become apparent that the degree of PPO activation could influence the mode and degree of protection. In conclusion, this review demonstrates that protein-bound phenols and encapsulation in protein-phenol complexes, induced by PPO-mediated diphenol oxidation, could be of interest when aiming to protect lipids against pre-ruminal and ruminal degradation.Keywords: red clover, polyphenol oxidase, lipid metabolism, rumen, silage ImplicationsPolyphenol oxidase (PPO) is an enzyme that has been found to be active in red clover. There is a whole range of recent studies exploring possibilities of using this enzyme to protect membrane lipids against degradation in the forage during storage and in the rumen of ruminants. Protection of lipids against degradation is of importance as it could help to improve the fatty acid profile of ruminant products, with respect to consumer health. This review aims to summarize...

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Section: Introductionmentioning

confidence: 99%

Red clover polyphenol oxidase and lipid metabolism

Ranst

Lee

Fievez

2011

Animal

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“…The main cause for browning in vegetables is the presence of polyphenol oxidases, which have been extensively studied and also found in yacon roots (MAYER, 1986;QUEIROZ et al, 2008;YORUK;MARSHALL, 2003;YOSHIDA et al, 2002). Neves and Da Silva (2007) studied the properties of polyphenol oxidases from yacon roots as well as its inactivation and response to inhibitors.…”

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Antioxidants in yacon products and effect of long term storage

et al. 2012

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Yacon (Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson) is a storage root originally grown in the Andean highlands. The fresh roots are perishable and quickly turn brown during handling and processing. Aiming to prolong shelf-life and to preserve the antioxidant compounds in yacon roots, 3 mm thick yacon slices were dried in a drying cabinet at 40, 50, and 60 ºC to a moisture content of 10-14%, and yacon strips were sun dried to a moisture content of 15-20%. The total phenolic content was measured by the Folin-Ciocalteu method, and the quenching capacity was evaluated by measuring the amount of DPPH (1,1-diphenyl-2-pidrylhydrazyl) inhibited in samples after drying and after 7 months of storage. The results showed that it is possible to preserve the antioxidant capacity in yacon after cabinet or sun drying. Both yacon chips and strips presented total phenolic content values similar to those of fresh yacon roots. Both products also showed a high inhibition capacity of DPPH (1,1-diphenyl-2-pidrylhydrazyl). A significant decrease in the phenolic content was observed in the yacon chips after storage, which indicates that the sun dried strips are more suitable for storage.

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“…They are plastid-localized copper metalloenzymes that catalyze the oxidation of o-diphenols to o-diquinones (diphenolase activity; EC 1.10.3.2) and, in some species, also the o-hydroxylation of monophenols (monophenolase activity; EC 1.14.18.1; Vaughn et al, 1988;Mayer, 2006). Quinones are highly reactive electrophiles responsible for much of the oxidative browning in fruits and vegetables after wounding (Yoruk and Marshall, 2003). The wound-inducible expression of PPOs has been reported in apple (Malus domestica; Boss et al, 1995), tomato (Solanum lycopersicum; Constabel et al, 1995;Thipyapong and Steffens 1997), potato (Solanum tuberosum; Thipyapong et al, 1995), and hybrid poplar (Populus spp.…”

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Polyphenoloxidase Silencing Affects Latex Coagulation in Taraxacum Species

et al. 2009

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Latex is the milky sap that is found in many different plants. It is produced by specialized cells known as laticifers and can comprise a mixture of proteins, carbohydrates, oils, secondary metabolites, and rubber that may help to prevent herbivory and protect wound sites against infection. The wound-induced browning of latex suggests that it contains one or more phenoloxidizing enzymes. Here, we present a comprehensive analysis of the major latex proteins from two dandelion species, Taraxacum officinale and Taraxacum kok-saghyz, and enzymatic studies showing that polyphenoloxidase (PPO) is responsible for latex browning. Electrophoretic analysis and amino-terminal sequencing of the most abundant proteins in the aqueous latex fraction revealed the presence of three PPO-related proteins generated by the proteolytic cleavage of a single precursor (pre-PPO). The laticifer-specific pre-PPO protein contains a transit peptide that can target reporter proteins into chloroplasts when constitutively expressed in dandelion protoplasts, perhaps indicating the presence of structures similar to plastids in laticifers, which lack genuine chloroplasts. Silencing the PPO gene by constitutive RNA interference in transgenic plants reduced PPO activity compared with wild-type controls, allowing T. kok-saghyz RNA interference lines to expel four to five times more latex than controls. Latex fluidity analysis in silenced plants showed a strong correlation between residual PPO activity and the coagulation rate, indicating that laticifer-specific PPO plays a major role in latex coagulation and wound sealing in dandelions. In contrast, very little PPO activity is found in the latex of the rubber tree Hevea brasiliensis, suggesting functional divergence of latex proteins during plant evolution.

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Physicochemical Properties and Function of Plant Polyphenol Oxidase: A Review

Cited by 505 publications

References 230 publications

Red clover polyphenol oxidase and lipid metabolism

Red clover polyphenol oxidase and lipid metabolism

Antioxidants in yacon products and effect of long term storage

Polyphenoloxidase Silencing Affects Latex Coagulation in Taraxacum Species

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