scorbate oxidase is a multi-copper enzyme that catalyzes the oxidation of ascorbic acid to dehydroascorbic acid. This copper containing blue enzyme is found in cucurbitaceous plants such as pumpkin, cucumber, and melon. It can eliminate ascorbic acid, which has high reducing power in clinical analyses, and detect levels of ascorbic acid. The biological function of ascorbate oxidase is still not clear. One suggestion is that the enzyme participates in a redox system involving ascorbic acids. It may be involved in the reorganization of the cell wall. In pumpkins, ascorbate oxidase expression increased rapidly during growth of callus, development of fruits, and elongation of seedlings. Ascorbate oxidase is present in young and growing tissues of tobacco. It is induced by phytohormone auxin which suggests that it is involved in cell growth.
Ascorbate oxidase consists of three spectroscopically distinct copper centers which comprise of one type I, one type II, and two type III copper atoms. The subunits of 552 residues are each built of three domains arranged sequentially on the polypeptide chain and tightly associated in space. Each subunit consists of four copper atoms bound as mononuclear and trinuclear species, type I and a combination of type II and type III respectively. The type 1 copper atom has two histidine (His), a cysteine (Cys), and an alkyl group (R) as ligands to the central copper atom and is located in domain three. The trinuclear cluster has eight histidine ligands symmetrically supplied from domains one and three and two oxygen atoms either bound as an alcohol (OH) or as a diatomic (O2). The cluster can be subdivided into two groups, the putative type III copper and the putative spectroscopic type II copper. The type II group consists of a single copper atom with two histidine ligands and an oxygen atom which is trans to the type III copper pair. A pair of copper atoms bounded to six histidines, three ligands on each copper. Bridged by the oxygen atom, the two coppers form the type III copper atom.
scorbate oxidase is a multi-copper enzyme that catalyzes the oxidation of ascorbic acid to dehydroascorbic acid. This copper containing blue enzyme is found in cucurbitaceous plants such as pumpkin, cucumber, and melon. It can eliminate ascorbic acid, which has high reducing power in clinical analyses, and detect levels of ascorbic acid. The biological function of ascorbate oxidase is still not clear. One suggestion is that the enzyme participates in a redox system involving ascorbic acids. It may be involved in the reorganization of the cell wall. In pumpkins, ascorbate oxidase expression increased rapidly during growth of callus, development of fruits, and elongation of seedlings. Ascorbate oxidase is present in young and growing tissues of tobacco. It is induced by phytohormone auxin which suggests that it is involved in cell growth.Ascorbate oxidase consists of three spectroscopically distinct copper centers which comprise of one type I, one type II, and two type III copper atoms. The subunits of 552 residues are each built of three domains arranged sequentially on the polypeptide chain and tightly associated in space. Each subunit consists of four copper atoms bound as mononuclear and trinuclear species, type I and a combination of type II and type III respectively. The type 1 copper atom has two histidine (His), a cysteine (Cys), and an alkyl group (R) as ligands to the central copper atom and is located in domain three. The trinuclear cluster has eight histidine ligands symmetrically supplied from domains one and three and two oxygen atoms either bound as an alcohol (OH) or as a diatomic (O2). The cluster can be subdivided into two groups, the putative type III copper and the putative spectroscopic type II copper. The type II group consists of a single copper atom with two histidine ligands and an oxygen atom which is trans to the type III copper pair. A pair of copper atoms bounded to six histidines, three ligands on each copper. Bridged by the oxygen atom, the two coppers form the type III copper atom.
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