The significance of AHCY in regulating the cellular methylation potential has been underscored by the discovery of AHCY deficiency in humans, a rare and potentially lethal multisystem disorder caused by allelic mutations in the AHCY gene that results in reduced AHCY enzymatic activity [1,7,8,9,10,11], with dramatically increased levels of metabolites SAH and SAM. This evidence concerns the gene AHCY and hyperinsulinemic hypoglycemia, familial, 4.