S-Adenosylhomocysteine hydrolase deficiency, also known as AdoHcy hydrolase deficiency or adenosylhomocysteinase (AHCY) deficiency, is an autosomal recessive disorder characterized by a defective AHCY gene. AHCY codes for the enzyme S-adenosylhomocysteine hydrolase (AdoHcyase) which efficiently eliminates S-adenosylhomocysteine (SAH) by catalyzing its hydrolysis into adenosine and homocysteine. SAH is both a byproduct of S-adenosylmethionine-dependent methyltransferases and a powerful methyltransferase inhibitor. For these reasons, AdoHcyase is thought to play an essential role in regulating methylations. AdoHcyase deficiency causes a buildup of homocysteine which may be then converted into methionine or cysteine. The accumulation of methionine as a result of AHCY deficiency may lead to signs and symptoms associated with hypermethioninemia, including mental and motor retardation, dysmorphism (unusual facial features), and abnormalities in liver function.

S-Adenosylhomocysteine (SAH) Hydrolase Deficiency References