Results 111 to 120 of about 2,050 (137)

High Pressure Inactivation of Polyphenoloxidases

Journal of Food Science, 1998
ABSTRACT Pressure stabilities of polyphenoloxidases (PPO) from apples, avocados, grapes, pears and plums were determined at pH 6‐7. These PPOs differed in pressure stability, but all were rather pressure‐stable. Inactivation of PPO from apple, grape, avocado and pear at room temperature (25°C) became noticeable at
C. WEEMAES, L. LUDIKHUYZE, I. VAN DEN BROECK, M. HENDRICKX   +3 more
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Tyrosinase and polyphenoloxidase. The role of metallic ions in melanogenesis

Biochimica et Biophysica Acta, 1951
Abstract A study was made to explain the different behaviour of animal and of vegetal polyphenol-oxidases on monohydric- and dihydric-phenols. 1. 1. It was found that the first phase of the tyrosine oxidation (the transformation of tyrosine in Dopa) is considerably accelerated by excess of copper, by cobalt, by vanadium and by nickel, whilst iron,
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Polyphenoloxidase from DeChaunac grapes

Journal of the Science of Food and Agriculture, 1983
AbstractPolyphenoloxidase (PPO) from red grape cultivar, DeChaunac, grown in New York State was isolated and purified 17‐fold by using Phenyl Sepharose CL‐4B column. Disc gel electrophoresis revealed near homogeneity of three isoenzyme bands. The molecular weight of this enzyme ranged from 73 000 to 85 000. The temperature and pH optima of the purified
C. Y. Lee, N. L. Smith, A. P. Pennesi
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Strawberry Polyphenoloxidase: Purification and Characterization

Journal of Food Science, 1990
ABSTRACT Stable and highly active polyphenoloxidase (PPO) extracts were obtained using polyvinylpyrrolidone, Amberlite XAD‐4, Triton X‐100, and protease inhibitor in pH 5.25 buffer. Citrate and phosphate prevented binding of PPO to pectin.
PEDRO WESCHE‐EBELING, MORRIS W. MONTGOMERY   +1 more
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Detection and Identification of the Polyphenoloxidase Substrate of the Banana

Nature, 1959
BLACKENING of the fruit of the banana may occur during cultivation, when the cause is usually of pathological origin, or during storage if ripening is not adequately controlled. The biochemical changes involved in the blackening of the fruit have received little study, although evidence for the existence of an enzyme system in the fruit of the banana ...
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The affinity for oxygen of polyphenoloxidase in grapes

Zeitschrift für Lebensmittel-Untersuchung und -Forschung, 1973
The influence of oxygen on the reaction of polyphenoloxidase in grapes was determined. Using crude extracts of grapes with a sufficiently high polyphenoloxidase activity on a substrate of pyrocatechol, apparentKm values for oxygen, at 25° C were calculated as 1.1 × 10−4mol (or 9% 02) for Sultana, and 1 × 10−4mol (or 8% O2) for Doradillo grapes.
F. Radler, E. Torokfalvy
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Localization of Polyphenoloxidase in the Chloroplasts of Beta vulgaris

Nature, 1948
THE chloroplast as the seat of chlorophyll pigments in plants occupies a unique position in the economy of the green cell. In recent years there has been a renewed interest in the reactions and properties of chloroplasts as a result of the work of Hill1,2 and Hill and Scarisbrick3,4, who demonstrated that the reaction characteristic of photosynthesis ...
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EPR Spectroskopy of Dog-Rose Polyphenoloxidase

1997
Polyphenoloxidase(PPO) of dog-rose fruit was extracted and purified through (NH4)(2)SO4 precipitation and dialysis. The optimum conditions for this purpose, i.e., pH and temperature, were determined with 4-methylcatechol optimum pH and temperature and found to be pH 8.5 and 20 degrees C, respectively.
Kufrevioglu, I, NUHOGLU, C, Sakiroglu, Halis, YOGURTCU, YK, UCUN, F, AYYILDIZ, Eyüp   +5 more
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Kinetics of reconstitution of polyphenoloxidase from apoenzyme and copper

Biochemical and Biophysical Research Communications, 1972
Abstract The EPR signal observed just after mixing apo-polyphenoloxidase and cupric copper decreases with a biphasic time course, while regain of enzymatic activity follows first order kinetics. These results may be explained by assuming that each catalytic site in polyphenoloxidase contains two non equivalent copper atoms.
D, Kertesz, G, Rotilio, M, Brunori, R, Zito, E, Antonini   +4 more
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Transient kinetic studies of dopa oxidation by polyphenoloxidase

Biochimica et Biophysica Acta (BBA) - Enzymology, 1971
The oxidation of DOPA (o-dihydroxyphenylalanine) to dopachrome as catalyzed by polyphenoloxidase (o-diphenol:O2 oxidoreductase, EC 1.10.3.1., also called tyrosinase) has been followed in transient-state experiments. The progress of the reaction depends on the wavelength of observation and in the spectral region where dopachrome is the major ...
D, Kertesz, M, Brunori, R, Zito, E, Antonini   +3 more
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