Hermes-Lima, M., Wang, E.M., Schulman, H.M., Storey, K.B. and Ponka, P. 1994. Deoxyribose degradation catalyzed by Fe(III)EDTA: kinetic aspects and potential usefulness for submicromolar iron measurements. Mol. Cell. Biochem. 137, 65-73.

Deoxyribose degradation catalyzed by Fe(III)EDTA: kinetic aspects and potential usefulness for submicromolar iron measurements

M. Hermes-Lima, E.M. Wang, H.M. Schulman, K.B. Storey and P. Ponka


Abstract
Iron ions play a central role in OH radicals formation and induction of oxidative stress in living organisms. Iron-catalyzed OH radical formation degrades deoxyribose to thiobarbituric acid reactive substances (TBA-RS). This paper analyzes kinetic properties of the Fe(III)-EDTA-catalyzed deoxyribose degradation in the presence of ascorbate. The yield of TBA-RS formation in the presence of EDTA was 4-fold higher than in its absence, contrasting with results reported elsewhere, Cu(II)-EDTA and Fe(III)-citrate were unable to catalyze deoxyribose degradation. The dependence on deoxyribose concentration was fitted to a Lineweaver Burk-like plot and it was calculated that approximately 4.5 mM deoxyribose scavenged half of the OH radicals formed. The data for Fe(III)-EDTA concentration dependence could also be fitted to a rectangular hyperbolic function. This function was linear up to 1 microM added FeCl3 and this property could be utilized as an assay for the estimation of submicromolar iron concentrations. Submicromolar concentrations of iron could induce measurable yields of TBA-RS. Differences of as little as 0.1 microM Fe(III)-EDTA could be reproducibly detected under optimum experimental conditions, above a consistent background absorbance that was equivalent to 0.35 + 0.05, microM Fe(III)-EDTA and represented contaminating iron in the reactants that could not be removed with Chelex-100. The low method determination limit makes the deoxyribose degradation reaction potentially useful as a new, highly sensitive and cost effective assay for iron quantification.