Distribution of Ascorbate Oxidase in Citrus Fruits

Abstract

Twenty cultivars of citrus fruit were harvested at two stages of development: young fruit (weight about 2.5 g per fruit) and fully ripe fruit of which the ascorbate oxidase (AAO) activities were determined. Among the different cultivars, the specific activity of AAO in the young fruits ranged from 47 to 2120 units per mg protein, while fully ripe fruits had AAO specific activity ranging from 18 to 97 units per mg protein. Significant differences were also observed between tissue types in the AAO specific activity with the highest activity in the albedo (64-70%), followed by the flavedo (26-34%) and the pulp (2-3%). Further examination of the seasonal changes in AAO specific activity in the peel (flavedo and albedo) of Satsuma mandarin fruit indicated the highest AAO activity when a fruit weight was between 2-4 g. The AAO activity then decreased as the fruit became more mature. Similar changes in the pattern of AAO specific activity were also observed for the different harvest years 1994 and 1995.