Distribution and Cellular Localization of Ascorbic Acid Oxidase in the Maize Root Tip

Abstract

Mertz, Dan. (U. Missouri, Columbia.) Distribution and cellular localization of ascorbic acid oxidase in the maize root tip. Amer. Jour. Bot. 48(5): 405–413. Illus. 1961.—Ascorbic acid oxidase has been identified by its various properties in homogenates of the maize root tip. Following centrifugal fractionation of the gross homogenate, approximately 30% of the total oxidase activity was found in the soluble fraction, while roughly 70% was bound to the cell wall debris. Quantitative measurements of serial segments revealed that the bound oxidase per cell increases with cell elongation. The very striking parallelism of the bound oxidase activity with that of cell elongation suggests that ascorbic acid oxidase may in some way participate in growth of the cell wall, and have very little to do with cellular respiration.

Ascorbate oxidase: The unexpected involvement of a ‘wasteful enzyme’ in the symbioses with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi

“…Between the 1960s and the beginning of the new century, the opinion prevailed that AO controls cell extension, although the actual mechanism of its action remained unknown [7], [8] and [9]. Gene expression analysis showed that the AO gene is induced by light [10] and [11].…”

Ascorbic Acid Oxidase in Cell Growth

“…The theory by the Milan group (14) that auxin pr,omotes growth by inhibiting ascorbic acid oxidation, fails to consider growth systems in which ascorbic acid oxidase has been shown to increase wvith rapidly growing cells (9,11,12). In the present study a comparison of ascorbic acid oxidase activity from maize mesocotyls was madle between dwarf-1, GA3-treated dwarf-1, and heterozygote normal.…”

“…While this theory and its supporting data are of considerable interest it does not explain the observation that the highest ascorbic acid oxidase activity in the maize root tip is associated with those cells wvhich are undergoing rapid cell elongation (9). Furthermore, Newcomb (11,12) has demonstrated that ascorbic acid oxidase activity is increased by auxin in tobacco pith tissue.…”

“…Ascorbic acid oxidase activity was determined as previously described (9). For ascorbic acid and dehydroascorbic acid determinations the tissue was homogenized in 3 % ice-cold, 0,-free metaphosphoric acid in an ice-jacketed Virtis-23 homogenizer or in a Waring blendor.…”

Ascorbic Acid Oxidase in Barley and Malt and Its Possible Role During Mashing

“…Honda studied the enzyme in barley roots and found it be associated with cell walls (9), in keeping with the findings of others (16). Tamas et al (24) studied the impact of cadmium on AAO in germinating barley seeds, with the agent causing substantial inhibition of rootlet growth.…”