Identification of the alpha and beta anomers of 1-(2-deoxy-D-erythro-pentofuranosyl)-oxaluric acid at the site of riboflavin-mediated photooxidation of guanine in 2'-deoxyguanosine and thymidylyl-(3'-5')-2'-deoxyguanosine.
Products of riboflavin-mediated photosensitization of 2'-deoxyguanosine (dG) and thymidylyl-(3'-5')-2'-deoxyguanosine (TpdG) by 350-nm light in oxygen-saturated aqueous solution have been isolated and identified as 1-(2-deoxy-beta-D-erythro-pentofuranosyl) oxaluric acid (beta-dOx) and thymidylyl-(3'-5')-1-(2-deoxy-beta-D-erythro-pentofuranosyl) oxaluric acid (Tpbeta-dOx), respectively. In aqueous solution the modified beta-deoxyribonucleoside is slowly converted to the alpha-anomer, generating alpha-dOx and Tpalpha-dOx. These modified nucleosides and dinucleoside monophosphates have been isolated by HPLC and characterized by proton and carbon NMR spectroscopy, fast atom bombardment mass spectrometry, and enzymatic analyses. Both alpha-dOx and Tpalpha-dOx slowly convert back into the modified beta-deoxyribonucleoside, indicating that the furanosidic anomers are in dynamic equilibrium. Relative to TpdG, the rate of hydrolysis of Tpbeta-dOx and Tpalpha-dOx by spleen phosphodiesterase is greatly reduced. Hot piperidine (1.0 M, 90 degrees C, 30 min) destroys Tpbeta-dOx and Tpalpha-dOx. Riboflavin-mediated photosensitization of TpdG in D2O instead of H2O has no detectable effect on the yield of Tpbeta-dOx, suggesting that oxaluric acid is generated through a Type-I reaction mechanism, likely through the intermediary on initially generated 8-oxo-7,8-dihydro-2'-deoxyguanosine.
Buchko
Garry W
GW
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA.
Cadet
Jean
J
D003849:Deoxyguanosine / Q000737:chemistry*; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D007700:Kinetics; D010100:Oxygen; D017319:Photosensitizing Agents; D012256:Riboflavin / Q000737:chemistry*; D012996:Solutions; D013237:Stereoisomerism; D013941:Thymine / Q000737:chemistry*
D015226:Dinucleoside Phosphates; D017319:Photosensitizing Agents; D012996:Solutions; C077117:thymidylyl-(3',5')-2'-deoxyguanosine; D006147:Guanine; D003849:Deoxyguanosine; D013941:Thymine; D010100:Oxygen; D012256:Riboflavin