Oxalic acid oxidase

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

TThe primary function of D-amino acid oxidase, present at high levels in the kidney, is thought to be the detoxification of ingested D-amino acids derived from bacterial cell walls and from cooked foodstuffs (heat causes some spontaneous racemization of the l-amino acids in proteins). Oxalate, whether obtained in foods or produced enzymatically in the kidneys, has medical significance. Crystals of calcium oxalate account for up to 75% of all kidney stones. ... 

Oxalate oxidase. In some instances, as in dry wine, there is not sufficient glucose to effect deoxygenation. However there appears to be sufficient oxalic acid in many wines to act as the substrate for combination with oxygen by oxalate oxidase, derived from the discarded leafy tops of the sugar beet plant (29). The application may still not work well if it relies on catalase to decompose the H2O2 formed by the oxidase, as catalase is strongly inhibited by ethanol at the pH of wine. 

FIGURE 10.41 DegrAdative pathways resulting in the foimation of Oxalic acid. The degradation of glycine and ethanolamlne to yield oxalic acid is catalyzed by oxidases. The breakdown of ascorbic add to produce oxalic and threonic acids occurs spontaneously over... 

Prompt stabilization of ascorbic acid is especially important in the case of plasma or serum samples. Metaphosphoric acid is often used for this purpose because it also serves as a protein precipitant. Such properties are desirable in the inactivation of oxidase and the catalytic eflFect of copper. Oxalic acid is an attractive stabilizer for ascorbic acid analysis because of its lower cost and greater stability however, it is not a protein precipitant, therefore, it has a limited use for the extraction of animal tissues. The use of ethylenediaminetetraacetic acid (EDTA) in addition to the metaphosphoric acid has been recommended (96). EDTA would chelate divalent cations, and a study has shown it will stabilize ascorbic acid in the presence of copper for several days (96). Perchloric acid has been used also but because of its inherent dangerous properties its use is generally avoided. Trichloroacetic acid and EDTA also seem appropriate extractants for ascorbate in plant materials (97). 

Why is the operational stability of an enzyme-based thermal sensor for oxalic acid expected to be poorer than an amperometric oxalate sensor prepared using the same enzyme, oxalate oxidase ... 

Oxalic acid poses a problem to both leafy plants and vertebrates because these organisms cannot catabolize it [108]. Although accumulation of oxalate leads to stress in plants, in vertebrates this molecule can be metaboHzed by bacteria present in the intestinal tract [109]. Oxalate can be catabolized in different ways by oxidation, by decarboxylation of oxalyl-coenzyme A or by direct decarboxylation. Both oxidation and decarboxylation of oxalate are catalyzed by Mn-containing enzymes. Here we will discuss the oxalate decarboxylate reaction that produces formate and CO2. The crystal structure of oxalate oxidase from Bacillus subtilis... 

Intermediate formation of qulnone derivatives and cytochrome oxidase via cytochrome C CBonner, 1957 Aberg, 1958 Mapson, 1958 Chlnoy, 1962 Chlnoy et al., 1969 1969 a 1970). In some cases these enzyme systems may readily oxidize all AA to DHA upon grinding while In other cases natural Inhibitors, e g, oxalic acid, strongly retard this process CAberg, 1958 Mapson, 1958). Hence a method for the determination of ascorbic acid utilization (AAU was developed ... 

In honey gluconic acid is in equilibrium with its gluconolactone. The acid level is mostly dependent on the time elapsed between nectar collection by bees and achievement of the final honey density in honeycomb cells. Glucose oxidase activity drops to a negligible level in thickened honey. Other acids present in honey only in small amounts are acetic, butyric, lactic, citric, succinic, formic, maleic, malic and oxalic acids. 

There a number of cases other than those of dihydroxyfumaric acid oxidase and tryptophan oxidase in which peroxidases appear to play the part of oxidases. These include indolylacetic acid oxidase and the related indolylpropionic and indolylbutyric acid oxidases (285, 415,416,618,733,777), the oxidase of oxalic, oxalacetic, ketomalonic, and dihydroxytartaric acids (414), of phenylacetaldehyde (413) and saturated fatty acid oxidase (711). 

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