Uric acid protection of nucleobases from ozone-induced degradation

doi:10.1016/0003-9861(86)90340-1

Archives of Biochemistry and Biophysics

Volume 246, Issue 2, 1 May 1986, Pages 838-845

https://doi.org/10.1016/0003-9861(86)90340-1 Get rights and content

Abstract

Uric acid has been proposed to be an important antioxidant and free radical scavenger in humans. Of the purine and pyrimidine compounds examined in this study, uric acid showed the greatest susceptibility to ozone-induced degradation. The parent compounds, purine and pyrimidine, were more resistant to ozonation than were the nucleobases. When the degradation of OH-substituted purines was examined, it was found that the more OH groups on the purine ring, the more readily the purine was degraded. Urea and allantoin were identified as degradation products of uric acid. The relative rates of nucleobase degradation in the presence and absence of uric acid were compared. Uric acid protected thymine, guanine, and uracil from degradation by ozone. In this system uric acid was found to protect the nucleobases as effectively as reduced glutathione.

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Synthesis of uranyl(II), vanadyl(II) and zirconyl urate complexes, spectral, thermal and biological studies
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Uric acid (C5H4N4O3) is a crystalline solid sparingly soluble in water and organic solvents [1] and is well known to exhibit antioxidant properties.
Three urate chelations were obtained when uric acid was reacted with UO₂(CH₃COO)₂H₂O, VOSO₄·XH₂O and ZrOCl₂·XH₂O salts with neutralized with 0.1 M NaOH aqueous media. The 1:2 metal-to-ligand complexes [(UO₂)₂(C₅H₂N₄O₃)₂](H₂O), [(ZrO)₂(H₂O)₂(C₅H₂N₄O₃)₂] and [VO((C₅H₃N₄O₃)₂] were characterized by elemental analyses, molar conductivity, (infrared, Raman and UV–vis) spectra, effective magnetic moment in Bohr magnetons, and thermal analysis (TG/DTG). The urate ligand coordinates as mononegative bidentate donor towards the mononuclear central vanadium atom and coordinated as binegative tetradentate mode towards the binuclear dioxouranium and zirconyl centers. The antibacterial activity of the metal complexes were tested against some kind of bacteria and fungi strains and compared with uric acid. The ligand, ZrO(II) and UO₂(II) complex showed a week potential degradation on calf thymus DNA, whereas VO(II) complex slightly degraded the DNA.
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The repair of tryptophan and tyrosine radicals in proteins by urate was studied by pulse radiolysis. In chymotrypsin, urate repairs tryptophan radicals efficiently with a rate constant of 2.7 × 10⁸ M^− 1 s^− 1, ca. 14 times higher than the rate constant derived for N-acetyltryptophan amide, 1.9 × 10⁷ M^− 1 s^− 1. In contrast, no repair of tryptophan radicals was observed in pepsin, which indicates a rate constant smaller than 6 × 10⁷ M^− 1 s^− 1. Urate repairs tyrosine radicals in pepsin with a rate constant of 3 × 10⁸ M^− 1 s^− 1―ca. 12 times smaller than the rate constant reported for free tyrosine―but not in chymotrypsin, which implies an upper limit of 1 × 10⁶ M^− 1 s^− 1 for the corresponding rate constant. Intra- and intermolecular electron transfer from tyrosine residues to tryptophan radicals is observed in both proteins, however, to different extents and with different rate constants. Urate inhibits electron transfer in chymotrypsin but not in pepsin. Our results suggest that urate repairs the first step on the long path to protein modification and prevents damage in vivo. It may prove to be a very important repair agent in tissue compartments where its concentration is higher than that of ascorbate. The product of such repair, the urate radical, can be reduced by ascorbate. Loss of ascorbate is then expected to be the net result, whereas urate is conserved.
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^☆: Alabama Agricultural Experiment Station Journal Series 4-84693. This research was supported by Hatch Project ALA 00573 and state funds of the Alabama Agricultural Experiment Station.

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Archives of Biochemistry and Biophysics

Abstract

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Cited by (39)

Comparison of pre-oxidation between O<inf>3</inf> and O<inf>3</inf>/H<inf>2</inf>O<inf>2</inf> for subsequent managed aquifer recharge using laboratory-scale columns

Synthesis of uranyl(II), vanadyl(II) and zirconyl urate complexes, spectral, thermal and biological studies

Fast repair of protein radicals by urate

Vibrational analysis of complexes of urate with IA group metal cations (Li<sup>+</sup>, Na<sup>+</sup> and K<sup>+</sup>)

Theoretical study of the acidity and basicity of uric acid and its interaction with water

Allantoin, the oxidation product of uric acid is present in chicken and turkey plasma

Uric acid protection of nucleobases from ozone-induced degradation☆

Abstract

Arch. Biochem. Biophys

Arch. Biochem. Biophys

Biochem. Pharmacol

Arch. Biochem. Biophys

Arch. Biochem. Biophys

Int. Rev. Cytol

Arch. Biochem. Biophys

Tetrahedron

Arch. Biochem. Biophys

J. Biol. Chem

Anal. Biochem

Biochim. Biophys. Acta

J. Lab. Clin. Med

Biochim. Biophys. Acta

Chem. Pharm. Bull