Catalyzes the hydrolysis of S-adenosyl-L-methionine (SAM) into adenosine and L-methionine (PubMed:18720493, PubMed:19739191). Is likely stereoselective, specifically hydrolyzing (R)-S-adenosyl-L-methionine ((R)-SAM), the inactive form of the ubiquitous cofactor SAM, and not the active form of SAM, (S)-S-adenosyl-L-methionine (By similarity). Probaly plays a role in preventing accumulation of (R)-S-adenosyl-L-methionine in cells; maintenance of (S)-S-denosyl-L-methionine homochirality is important for cellular health given that the (R)-form is largely inactive as a methyl donor and can function as an inhibitor of methyltransferases (By similarity). Shows very slow iodinase activity in vitro (PubMed:18720493). (R)-S-adenosyl-L-methionine + H2O = adenosine + H(+) + L-methionine Activity is inhibited by chloride. kcat is 0.5 min(-1) (PubMed:18720493). kcat is 0.45 min(-1) (PubMed:19739191). Optimum pH is 8. Belongs to the SAM hydrolase / SAM-dependent halogenase family.