ABSTRACT
Ascorbate oxidase (AO) is found in higher plants, but cucumber (Cucumis sativus) and green zucchini squash (Cucurbita pepo medullosa) are the most common sources. At the cellular level the enzyme is most abundant in the cell wall and the cytoplasm [20] , but its role in vivo is still under debate. The enzyme reduces ascorbate and other compounds that contain a lactone ring with an enediol group adjacent to a carbonyl group, as shown in Fig. 4. Since in vitro catechols and polyphenols are also substrates [21] , AO may be involved in biological processes such as fruit ripening. A role for plant respiration has also been suggested.
