Adenosylhomocysteinase (AHCY)

S-adenosylhomocysteine hydrolase belongs to the adenosylhomocysteinase family. It catalyzes the reversible hydrolysis of S-adenosylhomocysteine (AdoHcy) to adenosine (Ado) and L-homocysteine (Hcy). Thus, it regulates the intracellular S-adenosylhomocysteine (SAH) concentration thought to be important for transmethylation reactions. Deficiency in this protein is one of the different causes of hypermethioninemia.

In eukaryotes, this is the major route for disposal of the S-adenosylhomocysteine formed as a common product of each of many S-adenosylmethionine-dependent methyltransferases. The reaction is reversible, but under normal conditions the removal of both adenosine and homocysteine is sufficiently rapid to maintain the flux in the direction of hydrolysis.