A new procedure has been described for the isolation and purification of ascorbate oxidase from green zucchini squash (Cucurbita pepo meduttosa). The new purification method achieves a more than ZOO-fold purification with about a 14% recovery of the total activity present in the crude juice. The purified enzyme preparations have been found to be homogeneous by the criteria of ultracentrifugal a...

We evaluated the efficacies of five treatment procedures for eliminating ascorbate interference in the enzymatic determination of urinary oxalate. Aliquots of urine samples, containing different amounts of added ascorbate and oxalate, were individually subjected to ferric chloride, sodium nitrite, sodium periodate, charcoal, or ascorbate oxidase treatment to eliminate ascorbate interference. Ox...

Pretreatment of a serum or plasma sample with ascorbate oxidase removed interfering ascorbate and allowed the determination of cholesterol to be carried out by a current enzymatic cholesterol method available in kit form. The Cobas-Fara was programmed to carry out pretreatment of the sample with ascorbate oxidase before addition of the cholesterol colour reagent.

In an attempt to decrease ascorbate interference on the ion-chromatographic determination of urinary oxalate, we compared the effectiveness of four different methods for ascorbate elimination by analyzing a representative urine pool supplemented with successive ascorbate additions. Two of the methods--treatment with ferric ions or boric acid--have been described elsewhere; treatments with nitri...

The ascorbate oxidase activity of ceruloplasmin has been a subject of controversy because of (a) the relatively low oxidase activity of this serum copper protein toward ascorbic acid and (b) the different conclusions reached by several investigators. In 1951, Holmberg and Laurel1 (1) reported that ascorbic acid was a substrate of ceruloplasmin although it was less active as a substrate than p-p...

The interaction of one-electron reduced metronidazole (ArNO2.-) with native and Type-2-copper-depleted ascorbate oxidase were studied in buffered aqueous solution at pH 6.0 and 7.4 by using the technique of pulse radiolysis. With ArNO2.-, reduction of Type 1 copper of the native enzyme and of the Type-2-copper-depleted ascorbate oxidase occurs via a bimolecular step and at the same rate. Wherea...

Ascorbate is readily oxidized in aqueous solution by ascorbate oxidase. Ascorbate radicals are formed, which disproportionate to ascorbate and dehydroascorbic acid. Addition of erythrocytes with increasing intracellular ascorbate concentrations decreased the oxidation of ascorbate in a concentration-dependent manner. Concurrently, it was found, utilizing electron spin resonance spectroscopy, th...

The coordination environment of the type 2 (nonblue) copper in native ascorbate oxidase (L-ascorbate:oxygen oxidoreductase, EC 1.10.3.3) and of a derivative of the enzyme having the type 1 (blue) copper reversibly bleached has been examined by electron paramagnetic resonance (EPR) spectroscopy. In the g[unk] region of the spectrum of bleached ascorbate oxidase, a seven-line superhyperfine patte...

The respiratory components of the envelope membrane preparation of Neisseria meningitidis were investigated. Oxidase activities were demonstrated in this fraction in the presence of succinic acid, reduced nicotinamide adenine dinucleotide, and ascorbate-N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD). Differences in the kinetics of inhibition by terminal oxidase inhibitors on the three oxidase...