title: The oxidized forms of dATP are substrates for the human MutT homologue, the hMTH1 protein.
abstract: The possibility that Escherichia coli MutT and human MTH1 (hMTH1) hydrolyze oxidized DNA precursors other than 8-hydroxy-dGTP (8-OH-dGTP) was investigated. We report here that hMTH1 hydrolyzed 2-hydroxy-dATP (2-OH-dATP) and 8-hydroxy-dATP (8-OH-dATP), oxidized forms of dATP, but not (R)-8,5'-cyclo-dATP, 5-hydroxy-dCTP, and 5-formyl-dUTP. The kinetic parameters indicated that 2-OH-dATP was hydrolyzed more efficiently and with higher affinity than 8-OH-dGTP. 8-OH-dATP was hydrolyzed as efficiently as 8-OH-dGTP. The preferential hydrolysis of 2-OH-dATP over 8-OH-dGTP was observed at all of the pH values tested (pH 7.2 to pH 8.8). In particular, a 5-fold difference in the hydrolysis efficiencies for 2-OH-dATP over 8-OH-dGTP was found at pH 7.2. However, E. coli MutT had no hydrolysis activity for either 2-OH-dATP or 8-OH-dATP. Thus, E. coli MutT is an imperfect counterpart for hMTH1. Furthermore, we found that 2-hydroxy-dADP and 8-hydroxy-dGDP competitively inhibited both the 2-OH-dATP hydrolase and 8-OH-dGTP hydrolase activities of hMTH1. The inhibitory effects of 2-hydroxy-dADP were 3-fold stronger than those of 8-hydroxy-dGDP. These results suggest that the three damaged nucleotides share the same recognition site of hMTH1 and that it is a more important sanitization enzyme than expected thus far.
authors.affiliation: Department of Environmental Oncology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Fujikawa
authors.forename: H
authors.initials: H
authors.lastname: Kamiya
authors.forename: H
authors.initials: H
authors.lastname: Yakushiji
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.forename: Y
authors.initials: Y
authors.lastname: Nakabeppu
authors.forename: H
authors.initials: H
authors.lastname: Kasai
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D045643:DNA Repair Enzymes; D003838:Deoxyadenine Nucleotides / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011755:Pyrophosphatases; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D003838:Deoxyadenine Nucleotides; D029968:Escherichia coli Proteins; D010744:Phosphoric Monoester Hydrolases; D011755:Pyrophosphatases; C052211:mutT protein, E coli; C078207:8-oxodGTPase; D045643:DNA Repair Enzymes; C026600:2'-deoxyadenosine triphosphate