Allantoin precursors

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-... 

In more recent experiments in which the unidentified compound has been detected, it has coelectrophoresed with the ureide, allantoic acid (Figure 8). Allantoin, which is a precursor of allantoic acid in the purine degradation pathway of ureide synthesis, was not labeled significantly. 

Degradation of purine nucleotides was gauged by the labeling of the degradation end-product allantoin from nucleotides prelabeled with ( C) adenine, or during labeling with the purine precursor (l C) formate. 

In a short while, it was established that the precursors of nucleic acid purines were the same as those of uric acid. N -glycine was incorporated into adenine and guanine of the nucleic acids of growing yeast 28), and the earlier observations for uric acid precursors in the pigeon were confirmed for the nucleic acids of the rat 24). It has been substantiated in a variety of tissues that formate, glycine, and CO2 all contributed in major proportions to the synthesis of allantoin 25) and nucleic acid adenine and guanine... 

---