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Allantoin, uric acid oxidation

Fichter and Kern O first reported that uric acid could be electrochemically oxidized. The reaction was studied at a lead oxide electrode but without control of the anode potential. Under such uncontrolled conditions these workers found that in lithium carbonate solution at 40-60 °C a yield of approximately 70% of allantoin was obtained. In sulfuric acid solution a 63% yield of urea was obtained. A complete material balance was not obtained nor were any mechanistic details developed. In 1962 Smith and Elving 2) reported that uric acid gave a voltammetric oxidation peak at a wax-impregnated spectroscopic graphite electrode. Subsequently, Struck and Elving 3> examined the products of this oxidation and reported that in 1 M HOAc complete electrochemical oxidation required about 2.2 electrons per molecule of uric acid. The products formed were 0.25 mole C02,0.25 mole of allantoin or an allantoin precursor, 0.75 mole of urea, 0.3 mole of parabanic acid and 0.30 mole of alloxan per mole of uric acid oxidized. On the basis of these products a scheme was developed whereby uric acid (I, Fig. 1) is oxidized in a primary 2e process to a shortlived dicarbonium ion (Ha, lib, Fig. 1) which, being unstable, under-... [Pg.53]

Oxidation of Uric Acid.—Oxidation of uric acid in alkaline solution opens up the pyrimidine ring, producing allantoin. Oxidation in acid solution opens up the iminazole ring, producing alloxan. [Pg.346]

There is no doubt that electrochemically xanthine is initially oxidized to uric acid, which is then further oxidized to a bis-imine that undergoes hydrolysis giving ultimately alloxan, allantoin and urea. There is no single enzyme in man that will bring about such a fragmentation of xanthine. However, there are organisms that possess a combination of enzymes, e.g., xanthine oxidase and certain peroxidases, that under conditions comparable to those employed in the... [Pg.77]

In the case of the methylated xanthines, particularly theophylline, theobromine and caffeine, the preponderance of data on the metabolism of these compounds in man suggests that a methylated uric acid is the principal product. However, the data presented earlier proposes at best a 77 per cent accounting of the methylated xanthine administered. The question can be raised as to whether the final products observed upon electrochemical oxidation of these compounds aids these studies. Very recently studies of metabolism of caffeine have revealed that 3,6,8-trimethylallantoin is a metabolite of caffeine 48>. This methylated allantoin is, of course, a major product observed electrochemically. The mechanism developed for the electrochemical oxidation seems to nicely rationalize the observed products and electrochemical behavior. The mechanism of biological oxidation could well be very similar, although insufficient work has yet been performed to come to any definite conclusions. There is however, one major difference between the electrochemical and biological reactions which is concerned with the fact that in the former situation no demethylation occurs whereas in the latter systems considerable demethylation appears to take place. [Pg.78]

Purine metabolism in some mammals is characterized by a further oxidation of uric acid to al-lantoin by the enzyme urate oxidase. Allantoin is significantly more water soluble than uric acid and is also freely excreted via the renal route. [Pg.362]

Degradation of dietary nucleic acids occurs in the small intestine, where a family of pancreatic enzymes hydrolyzes the nucleotides to nucleosides and free bases. Inside cells, purine nucleotides are sequentially degraded by specific enzymes, with uric acid as the end product of this pathway. [Note Mammals other than primates oxidize uric acid further to allantoin, which, in some animals other than mammals, may be further degraded to urea or ammonia.]... [Pg.296]

Mammals other than primates further oxidize urate by a liver enzyme, urate oxidase. The product, allantoin, is excreted. Humans and other primates, as well as birds, lack urate oxidase and hence excrete uric acid as the final product of purine catabolism. In many animals other than mammals, allantoin is metabolized further to other products that are excreted Allantoic acid (some teleost fish), urea (most fishes, amphibians, some mollusks), and ammonia (some marine invertebrates, crustaceans, etc.). This pathway of further purine breakdown is shown in figure 23.22. [Pg.555]

Degradation of uric acid to excretory products. Mammals other than primates oxidize uric acid further to allantoin. Humans and other primates as well as birds lack urate oxidase and hence excrete uric... [Pg.556]

Moreover, the oxidation of methional to ethylene has been proposed (Beauchamp and Fridovich 1970 Biaglow et al. 1997), and the formation of allantoin (Grootveld and Halliwell 1987 Halliwell et al. 1988) from uric acid as well as the imidazolone derivative from histamine (Ching et al. 1995) have been suggested as an index of OH action in vivo (Halliwell et al. 1988). [Pg.66]

Grinstead RR (1960) Oxidation of salicylate by the model peroxidase catalyst iron-ethylenediamine-tetraacetato-iron(lll) acid. J Am Chem Soc 82 3472-3476 Grootveld M, Halliwell B (1987) Measurement of allantoin and uric acid in human body fluids. Bio-chemJ 243 803-808... [Pg.72]

Amino acids, amino groups, amino sugars, and nucleic acid derivatives usually account for >95% of the organic N in soils (Anderson et al., 1989), and many other N-containing compounds have been reported in trace amounts (Stevenson, 1994). Anderson et al. (1989) have found traces of L-phosphatidic acid, choline, ethanol-amine, and uric acid (the end product of N metabolism of many animals), which can be oxidized to allantoin, cyanuric acid, and urea. [Pg.26]

Purines and pyrimidines in excess of cellular requirements can be degraded. The extent of degradation depends on the organism. Humans cannot degrade purines beyond uric acid because we lack the enzyme uricase, which splits the purine ring to form allantoin. In humans excess AMP is deaminated to IMP by the action of a specific deaminase. IMP is then hydrolyzed by 5 -nucleotidase to form inosine. Inosine and guanine are oxidized to urate as follows ... [Pg.447]

The isolation of allantoin (7), after lead peroxide oxidation of uric acid was followed by the recognition of other oxidation products, the main product of which are oxonic acid (8), allantoxaidine (9) and oxaluric acid (HjNOCHNCOCOjH). Their structures have been clarified by comprehensive studies using isotopically labeled compounds. ... [Pg.541]

One of the first facts observed in regard to uric acid was that on heating it yielded cyanuric acid, (OCNH)3, and ammonia, NH3. As these same products had been obtained by heating urea, OC(NH2)2, it was considered probable that a urea residue was present in uric acid. It was then shown that on oxidation with lead dioxide, one of the ureids, the di-ureid known as allantoin was obtained, together with urea, oxalic acid and carbon dioxide. With other oxidizing agents, such as nitric acid, the products were equal molecules of urea and the two ureids alloxan and parabanic acid. From alloxan there may be obtained, by reduction, two other ureids, viz., barbituric acid and... [Pg.442]

Oxidation of uric acid (LXIV) and its iV-methylated derivatives at a graphite anode produces a quinonoid product (LXV), which adds water or another nucleophile across a C=N double bond to an unstable intermediate (LXVI), which reacts to products. From the oxidation of uric acid can be isolated, depending on pH, allantoin, 5-hydroxyhydan-toin, alloxan, and urea [362, 363] ... [Pg.701]

Allantoin has been prepared by the oxidation of uric acid with potassium permanganate/ lead dioxide/ potassium ferri-cyanide/ oxygen/ manganese dioxide/ ozone, hydrogen peroxide/ and by the electrolytic oxidation of lithium urate. It is also formed by heating glyoxylic acid with urea. ... [Pg.65]

The enzyme used for the assay of uric acid is uricase (urate oxidase, EC 1.7.3.3) which catalyzes the oxidation of uric acid to allantoin, CO2, and H2O2 ... [Pg.150]

Enzymatic methods generally offer greater specificity over conventional non-enzymatic colorimetric methods for the measurement of uric acid. Even so, methods that depend upon the use of oxidizing agents—such as phosphotungstic acid to oxidize uric acid to allantoin and carbon dioxide, and the resulting reduction of... [Pg.145]

Rasbnricase is an antimetabolite that catalyzes enzymatic oxidation of nric acid into an inactive and soluble metabolite (allantoin). It is indicated in initial management of plasma nric acid levels in pediatric patients with leukemia, lymphoma, and solid tnmor malignancies who are receiving anticancer therapy expected to result in tumor lysis and snbsequent elevation of plasma uric acid. [Pg.616]

Uric acid, the end point of purine degradation in primates, is excreted. Most other animals, however, oxidize uric acid to allantoin, hydrolyze allantoin to allantoic acid and subsequently convert allantoic acid to urea or other possible excretion products, depending on the animal (Figure 22.8). [Pg.747]

Oxidation of uric acid in non-primate animals yields allantoin. [Pg.2303]


See other pages where Allantoin, uric acid oxidation is mentioned: [Pg.157]    [Pg.58]    [Pg.414]    [Pg.102]    [Pg.54]    [Pg.57]    [Pg.59]    [Pg.59]    [Pg.61]    [Pg.62]    [Pg.64]    [Pg.64]    [Pg.65]    [Pg.268]    [Pg.43]    [Pg.625]    [Pg.625]    [Pg.1459]    [Pg.178]    [Pg.39]    [Pg.195]    [Pg.44]    [Pg.79]    [Pg.2505]    [Pg.146]    [Pg.282]    [Pg.546]   
See also in sourсe #XX -- [ Pg.625 ]




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