Oxalate production

It is apparent from DTA studies [1021] of the decompositions of Group IA formates in inert or oxidizing atmospheres that reaction is either preceded by or accompanied by melting. Anion breakdown leading to carbonate production may involve formation of the oxalate, through dimerization [1022] of the postulated intermediate, C02, especially during reaction of the Na and K salts in an inert atmosphere and under isothermal conditions. Oxalate production is negligible in reactions of the Li and Cs formates. Reference to oxalate formation is included here since this possibility has seldom been considered [1014] in discussions of the mechanisms of decompositions of solid formates. 

Li H-Q, 1 Matsuda, Y Eujise, A Ichiyama (1999) Short-chain acyl-CoA-dependent production of oxalate from oxaloacetate by Burkholderia glumae, a plant pathogen which causes grain rot and seedling rot of rice via oxalate production. J Biochem 126 243-253. 

From Figure 2.114, it can be seen that the oxalate production was always delayed somewhat with respect to both CO - and glycolate. The authors postulated that this was as a result of the desorption and then subsequent re-adsorption, of glycolate. 

Eggins and McNeill compared the solvents of water, dimethylsulfoxide (DMSO), acetonitrile, propylene carbonate, and DMF electrolytes for C02 reduction at glassy carbon, Hg, Pt, Au, and Pb electrodes [78], The main products were CO and oxalate in the organic solvents, while metal electrodes (such as Pt) which absorb C02 showed a higher production for CO. In DMF, containing 0.1 M tetrabutyl ammonium perchlorate and 0.02 M C02 at a Hg electrode, Isse et al. produced oxalate and CO with faradaic efficiencies of 84% and 1.7%, respectively [79], Similarly, Ito et al. examined a survey of metals for C02 reduction in nonaqueous solution, and found that Hg, Tl, and Pb yielded primarily oxalate, while Cu, Zn, In, Sn, and Au gave CO [80, 81]. Kaiser and Heitz examined Hg and steel (Cr/Ni/Mo, 18 10 2%) electrodes to produce oxalate with 61% faradaic efficiency at 6 mA cm-2 [82]. For this, they examined the reduction of C02 at electrodes where C02 and reduction products do not readily adsorb. The production of oxalate was therefore explained by a high concentration of C02 radical anions, COi, close to the surface. Dimerization resulted in oxalate production rather than CO formation. 

Dutton, M. V. Evans, C. S. (1996). Oxalate production by fungi its role in pathogenicity and ecology in the soil environment. Caimdian Journal of Microbiology, 42, 881-95. 

Ahonen-Jonnarth et al., 2000) appear to be more efficient than taxa with low oxalate production in dissolving minerals containing phosphorus such as apatite (Wallander, 2000a)... 

Cerrano, C., Bravestrello, G., Arillo, A., Benatti, U., Bonpadre, S., Cattaneo-Vietti, R., Gaggero, L., Giovine, M., Leone, L., Lucchetti, G., and Sara, M., 1999, Calcium oxalate production in the marine sponge Chondrosia reniformis. Mar. Ecol. Prog. Ser. 179 297-300. 

Figure 1. Schematic overview of cellular oxalate production...

Jarosz-Wilkolazka, A., and Gadd, G. M. (2003). Oxalate production by wood-rotting fungi growing in toxic metal-amended medium. Chemosphere 52, 541-547. 

The same authors have shown that oxalate nephrocalcinosis and hyperoxaluria can be reproduced in animals such as rats (G6) or cats (G7) by vitamin Be deficiency. The main difference between the experimental disease and patients with oxalosis is the absence of extrarenal deposits in the former (G7). The urinary excretion of oxalate in vitamin Be-deflcient rats can be enhanced by dietary supplementation with vitamin Be antagonists, such as deoxypyridoxine or isonicotinic hydra-zide, or with glycine, which appears to be the endogenous source of the excessive oxalate production, as in patients with oxalosis (G6). 

These findings are of primary interest, as they might relate abnormal oxalate production in hiunans to vitamin Be deficiency. It has been found, for instance, that vitamin Be supplements decreased oxalate excretion in human subjects receiving diets which seemed more than adequate in vitamin Be (G7). The role of vitamin Be in the production of primary hyperoxaluria and oxalosis in human subjects has, however, not been demonstrated. 

Fig.2. Oxalic acid. Metabolic sources of oxalate. 2-Hydroxy-3-oxoadipate is a normal excretory product in humans, which diverts glyoxylate from oxalate production (see Inborn errors of metabolism. Oxalosis).

This interaction of the negative charge of the radical anion with the adsorbed cations results in significantly more positive potentials for CO2 reduction. In this case, oxalate production is also thought to occur by dimerization of adsorbed radical anions rather than dimerization of C02 radical anions in solution. Similar studies at lead electrodes have also been reported [30]. 

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