Abstract
Cell extracts from M. luteus release both free 3-methyladenine and free 7-methylguanine from alkylated [calf thymus] DNA. The glycosylase activity responsible for the liberation of 7-methylguanine is not 3-methyladenine-DNA glycosylase, which, when purified, does not liberate it. The heat inactivation rates of the 2 enzymatic activities are different. The release of 7-methylguanine by chemical depurination of ethanol-soluble oligonucleotides was ruled out. A similar activity releasing 7-methylguanine is also found in E. coli.