Evidence about the catecholoxidase activity of the enzyme ascorbate oxidase extracted from Cucurbita pepo medullosa.
Pure ascorbate oxidase (L-ascorbate:oxygen oxidoreductase, EC 1.10.3.3) isolated from Cucurbita pepo medullosa, which is known to be specific for ascorbic acid, shows a secondary catecholoxidase activity at approx. pH 6.7. This activity was tested against natural and synthetic compounds possessing a catechol-like structure. Among natural compounds (+)-catechin furnishes the same complex oxidation mixture obtained with other oxidases. Among synthetic compounds, 3,5-di-t-butylcatechol and 4-t-butylcatechol give the corresponding o-quinones. The significance of this secondary activity in the darkening process of fruits and vegetables which contain ascorbate oxidase is also discussed.
D001204:Ascorbate Oxidase / Q000378:metabolism*; D002392:Catechin / Q000378:metabolism; D002396:Catechols / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010088:Oxidoreductases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology; D013379:Substrate Specificity
D002396:Catechols; D002392:Catechin; D010088:Oxidoreductases; D001204:Ascorbate Oxidase