– Catalyzes the irreversible cleavage of the glycosidic bond in both 5′-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH/AdoHcy) to adenine and the corresponding thioribose, 5′-methylthioribose and S-ribosylhomocysteine, respectively. Also cleaves 5′-deoxyadenosine, a toxic by-product of radical S-adenosylmethionine (SAM) enzymes, into 5-deoxyribose and adenine. Thus, is required for in vivo function of the radical SAM enzymes biotin synthase and lipoic acid synthase, that are inhibited by 5′-deoxyadenosine accumulation.