ABSTRACT
Adenosine kinase (ADK) deficiency was first described in 2011, the result of an exome sequencing study in six patients from families with global retardation, epilepsy, hepatic dysfunction, dysmorphic features and hypermethioninemia. Direct phosphorylation of adenosine by ADK is a major route for the recycling of adenosine. Defective activity of the enzyme leads to accumulation of adenosine. ADK converts adenosine to adenosine monophosphate, and defective function of the enzyme leads to an accumulation of adenosine. Adenosine is elevated in dried blood spots from affected neonates and could be potentially used as a biomarker in newborn screening. A defective function of the enzyme leads to an accumulation of adenosine and reverses the reaction balance of S-adenosylhomocysteine hydrolase, causing elevated concentrations of S-adenosylhomocysteine, S-adenosylmethionine, and methionine, which are the biochemical hallmarks of the disease. Interference with a wide range of methyltransferases was deemed.
