Results 221 to 230 of about 7,808 (255)

Oxidation of the Flavonol Quercetin by Polyphenol Oxidase

Journal of Agricultural and Food Chemistry, 1998
Because direct oxidation of flavonols by polyphenol oxidase (PPO) has not previously been reported and, given the importance of flavonols, the ability of broad bean seed PPO to oxidize the flavonol quercetin was studied. The reaction was followed by recording spectral changes with time. Maximal spectral changes were observed at 291 nm (increase) and at
M, Jiménez, F, García-Carmona
openaire   +2 more sources

Polyphenol oxidases and peroxidases in fruits and vegetables

C R C Critical Reviews in Food Science and Nutrition, 1981
Polyphenol oxidases and peroxidases are among the most studied enzymes in fruits and vegetables. Owing to the deleterious effects of discoloration and off-flavor formation induced by their actions, these enzymes have not ceased to be a matter of concern to food technologists, while their versatility as catalyst and their diversity as protein present a ...
Lilly Vámos‐Vigyázó, Norman F. Haard   +1 more
openaire   +2 more sources

Properties of wheat bran polyphenol oxidase

Food / Nahrung, 2004
AbstractPolyphenol oxidase (PPO) obtained from wheat bran catalyzed the oxidation of 4‐methyl catechol. Phenolic compounds found naturally in crude extract played role as an endogeneous substrate and activity of crude extract needed correction. Activity versus enzyme concentration gave a linear plot at high substrate concentration whereas a nonlinear ...
Ciğdem, Soysal, Zerrin, Söylemez
openaire   +2 more sources

Unfolding and refolding of active apple polyphenol oxidase [PDF]

Phytochemistry, 1998
For the first time, unfolding (6 M guanidine) and refolding of partially proteolysed purified polyphenol oxidase (PPOr) was achieved, with 88% of activity recovered. Optimal refolding conditions consisted in stepwise dialysis of guanidine treated extracts, the dialysis buffers containing 1 M (NH4)2SO4 and 100 microM CuSO4.
Mari, Stéphane, Marquès, Laurence, Breton, Frédéric, Karamanos, Yannis, Macheix, Jean-Jacques   +4 more
openaire   +2 more sources

Degradation of Pentachlorophenol by Potato Polyphenol Oxidase

Journal of Agricultural and Food Chemistry, 2011
In this study, polyphenol oxidase (PPO) was extracted from commercial potatoes. Degradation of pentachlorophenol by potato PPO was investigated. The experimental results show that potato PPO is more active in weak acid than in basic condition and that the optimum pH for the reaction is 5.0.
Mei-Fang, Hou, Xiao-Yan, Tang, Wei-De, Zhang, Lin, Liao, Hong-Fu, Wan   +4 more
openaire   +2 more sources

Preharvest changes in polyphenols, peroxidase, and polyphenol oxidase in sorghum grain

Journal of Agricultural and Food Chemistry, 1981
At various stages of preharvest development. "bird-resistant" sorghum (Sorghum bicolor (I,.) Moench] grain was analyzed for tannin content and polyphenol oxidizing enzymes. Tannins appeared first at the milk stage, reached a maximum at the hard dough stage, and thereafter declined by 25%. Polyphenol oxidase (PPO) and peroxidase activities were detected
openaire   +2 more sources

A new insight into purification of polyphenol oxidase and inhibition effect of curcumin and quercetin on potato polyphenol oxidase

Protein Expression and Purification, 2020
In the literature, the polyphenol oxidase (PPO) enzyme has been purified a many times via Sepharose 4B-l-tyrosine-p-aminobenzoic acid affinity column. In order to study PPO purification efficiency, 2-aminophenol and 4-aminophenol were applied as a spacer arm to CNBr-activated Sepharose 4B.
openaire   +3 more sources

CYSTEINE AS AN INHIBITOR OF POLYPHENOL OXIDASE

Journal of Food Biochemistry, 1989
The effect of L-cysteine on mushroom polyphenol oxidase (PPO) activity was investigated using three spectrophotometric assays. The formation of pigment (melanin), o-phenylquinone and cysteine-quinone adduct from catechol were each assayed under similar conditions. Cysteine had two effects; first, a lag phase was seen when melanin formation was measured,
EVERETT D. DUDLEY, JOSEPH H. HOTCHKISS
openaire   +1 more source

New Spectrophotometric Assay for Polyphenol Oxidase Activity

Analytical Biochemistry, 1993
We describe a convenient and sensitive assay of polyphenol oxidase (PPO, EC 1.14.18.1) consisting of spectrophotometry at 300 nm based on the stoichiometric reaction of cysteine with o-quinones produced during the enzymatic oxidation of phenols. The adduct formed exhibited spectral properties different from those of the parent phenol.
Gauillard, Frederic, Forget, Florence, Nicolas, J.   +2 more
openaire   +3 more sources

Inhibition of Polyphenol Oxidases Activity by Various Dipeptides

Journal of Agricultural and Food Chemistry, 2004
In an effort to develop natural and nontoxic inhibitors on the activity of mushroom polyphenol oxidase (PPO) the effect of various glycyl-dipeptides (GlyAsp, GlyGly, GlyHis, GlyLeu, GlyLys, GlyPhe, GlyPro, GlyTyr) was investigated. The inhibition study with dihydroxyphenylalanine (DOPA) as substrate is based on separation of the enzymatic reaction ...
GIRELLI, Anna Maria, Enrico Mattei, MESSINA, Antonella, TAROLA, Anna Maria   +3 more
openaire   +3 more sources