Catalyzes the deamination of 5-methylthioadenosine and S-adenosyl-L-homocysteine into 5-methylthioinosine and S-inosyl-L-homocysteine, respectively. Is also able to deaminate adenosine. Adenosine-5-monophosphate (AMP) and S-adenosyl-L-methionine (SAM) are not enzyme substrates. H(+) + H2O + S-adenosyl-L-homocysteine = NH4(+) + S-inosyl-L-homocysteine H(+) + H2O + S-methyl-5'-thioadenosine = NH4(+) + S-methyl-5'-thioinosine Binds 1 zinc ion per subunit. Belongs to the metallo-dependent hydrolases superfamily. MTA/SAH deaminase family.