S-methyl-5'-thioadenosine deaminase (, MTA deaminase, 5-methylthioadenosine deaminase) is an enzyme with systematic name S-methyl-5'-thioadenosine amidohydrolase. This enzyme catalyses the following chemical reaction
The enzyme from Thermotoga maritima also functions as S-adenosylhomocysteine deaminase (EC 3.5.4.28).