This model represents the enzyme 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase which acts on its two substrates at the same active site. This clade of sequences is sufficiently distinct from the characterized proteins, which form the seed of TIGR01704 as to cast some doubt on the accuracy of annotations based on sequence similarity alone. This enzyme is involved in the recycling of the components of S-adenosylmethionine after it has donated one of its two non-ribose sulfur ligands to an acceptor. In the case of 5'-methylthioadenosine this represents the first step of the methionine salvage pathway in bacteria. This enzyme is widely distributed in bacteria.