title: Kinetic and thermodynamic analysis of the hydrolytic ring-opening of the malondialdehyde-deoxyguanosine adduct, 3-(2'-deoxy-beta-D-erythro-pentofuranosyl)- pyrimido[1,2-alpha]purin-10(3H)-one.
abstract: 3-(2'-Deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-alpha]purin-10(3H)-one (M1dG) is the major reaction product of deoxyguanosine with malondialdehyde or base propenals. M1dG undergoes hydrolytic ring-opening to N2-oxopropenyl-deoxyguanosine (N2OPdG) under basic conditions. We report that ring-opening of M1dG as a nucleoside or in oligonucleotides is a reversible second-order reaction with hydroxide ion. NMR and UV analysis revealed N2OPdG(-) to be the only product of M1dG ring-opening in basic solution. The rate constant for reaction of M1dG with hydroxide is 3.8 M(-1) s(-1), and the equilibrium constant is calculated to be 2.1 +/- 0.3 x 10(4) M(-1) at 25 degrees C. Equilibrium constants determined by spectroscopic analysis of the reaction end-point or by thermodynamic analysis of rate constants determined over a range of temperatures yielded a value 2.5 +/- 0.2 x 10(4) M(-1). Kinetic analysis of ring-opening of M1dG in oligonucleotides indicated the rate constant for ring-opening is decreased 10-fold compared to that in the nucleoside. Flanking purines or pyrimidines did not significantly alter the rate constants for ring-opening, but purines flanking M1dG enhanced the rate constant for the reverse reaction. A mechanism is proposed for ring-opening of M1dG under basic conditions and a role is proposed for duplex DNA in accelerating the rate of ring-opening of M1dG at neutral pH.
authors.affiliation: A. B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
authors.forename: James N
authors.initials: JN
authors.lastname: Riggins
authors.forename: J Scott
authors.initials: JS
authors.lastname: Daniels
authors.forename: Carol A
authors.initials: CA
authors.lastname: Rouzer
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Marnett
mesh_terms: D018736:DNA Adducts / Q000737:chemistry*; D003849:Deoxyguanosine / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008315:Malondialdehyde / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry*; D011684:Purine Nucleosides; D011687:Purines / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: C491625:3-(2'-deoxy-beta-D-erythro-pentofuranosyl)pyrimido(1,2-alpha)purin-10(3H)-one; D018736:DNA Adducts; D009841:Oligonucleotides; D009844:Oligosaccharides; D011684:Purine Nucleosides; D011687:Purines; D011743:Pyrimidines; D008315:Malondialdehyde; D003849:Deoxyguanosine