Isolation of 8-oxoguanine-DNA glycosylase from Escherichia coli and studies on its substrate specificity

A procedure for isolating electrophoretically homogeneous 8-oxoguanine-DNA glycosylase [EC 3.2.2] from E. coli was elaborated. Purification of the enzyme included a minimum number of stages. Enzyme preparations contained no impurities that cleave nucleic acids. The enzyme possessed two types of activity, 8-oxoguanine glycosylase and associated apurinic/apyramidinic endonuclease activities.For a number of double-stranded oligonucleotides (23 base pairs) that contain 8-oxoG at various positions in one of the strands, estimates were obtained for the Michaelis constant and maximal rates of the reaction catalyzed by the glycosylase. The dependence of the above-mentioned parameters on the position of 8-oxoG in the duplex was elucidated.