Catalysis of the reaction: DNA containing 7-methyladenine + H2O = DNA with abasic site + 7-methyladenine. This reaction is the hydrolysis of DNA by cleavage of the N-C1' glycosidic bond between the damaged DNA 7-methyladenine and the deoxyribose sugar to remove the 7-methyladenine, leaving an abasic site.
DNA-7-methyladenine glycosylase activity