AHCY,also named as SAHH,belongs to the adenosylhomocysteinase family. AHCY is a competitive inhibitor of S-adenosyl-L-methionine-dependent methyl transferase reactions; therefore AHCY may play a key role in the control of methylations via regulation of the intracellular concentration of adenosylhomocysteine. AHCY catalyzes the reversible hydrolysis of S-adenosylhomocysteine to adenosine and L-homocysteine..