R. Cathcart, D. Goldthwait
Jan 20, 1981
Citations
0
Influential Citations
55
Citations
Quality indicators
Journal
Biochemistry
Abstract
A 3-methyladenine-DNA N-glycosylase was identified in both nuclear and cytoplasmic extracts of rat liver. The enzyme was purified from nuclei due to a lower level of nonspecific nucleases. The enzyme was purified 100-fold by using DNA-cellulose and phosphocellulose chromatography. Several methods of assay were developed and are discussed. The molecular weight of the glycosylase was 24000. It exhibited a preference for double-stranded alkylated DNA. The apparent K/sub m/ for 3-methyladenine residues was 2.6 nM. The enzyme was shown to be a glycosylase by the stoichiometric release of 3-methyladenine and the appearance of alkali-sensitive sites. There was no endonucleolytic activity on double-stranded DNA, depurinated DNA, UV-treated DNA, or ..gamma..-irradiated DNA. The relative rate of release of 3-methyladenine and 7-methylguanine was the same for both the DNA-cellulose and phosphocellulose fractions, and both activities were inactivated by heat to the same extent. Whether one or two enzymes are involved is not known. The preparation does not release 3-methylguanine or 1-methyladenine.