DNA Glycosylases in DNA Repair
The excision of potentially mutagenic and lethal lesions from DNA proceeds by one of two different routes. DNA damage which results in a major distortion of the DNA double-helix is generally recognized by a high-molecular weight nuclease that cuts two phosphodiester bonds in the altered strand, one on each side of the lesion. While the biochemical properties of the complex E. coli enzyme catalyzing this reaction are being elucidated rapidly,1–3 the apparently analogous eukaryotic enzyme activity has not yet been demonstrated in a cell-free extract. The alternative pathway of excision-repair is initiated by one of several DNA glycosylases, which catalyze cleavage of the base-sugar bond of an altered nucleotide residue to release the damaged base component in free form and leave a repairable apurinic or apyrimidinic site in the DNA. The properties of DNA glycosylases have been reviewed.4–7 Some recent observations on the multiplicity and substrate specificity of these enzymes are discussed here; references to previous work may be found in the review cited.
KeywordsPhosphodiester Bond Micrococcus Luteus Mammalian Enzyme Adenine Residue alkA Gene
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