Identification of the Nucleotidase Responsible for the AMP Hydrolysing Hyperactivity Associated with Neurological and Developmental Disorders
Nucleoside monophosphate phosphohydrolases comprise a family of enzymes dephosphorylating nucleotides both in intracellular and extracellular compartments. Members of this family exhibit different sequence, location, substrate specificity and regulation. Besides the ectosolic 5′-nucleotidase, several cytosolic and one mitochondrial enzymes have been described. Nevertheless, researchers refer any AMP-dephosphorylating activity to as 5′-nucleotidase, lacking a more accurate identification. Increase of AMP hydrolysing activity has been associated with neurological and developmental disorders. The identification of the specific enzyme involved in these pathologies would be fundamental for the comprehension of the linkage between the enzyme activity alteration and brain functions. We demonstrate that the described neurological symptoms are associated with increased ectosolic 5′-nucleotidase activity on the basis of radiochemical assays and immunoblotting analysis. Furthermore, present data evidence that the assay conditions normally applied for the determination of cytosolic 5′-nucleotidases activity in crude extracts are affected by the presence of solubilised ectosolic nucleotidase.
Keywords5′-Nucleotidase Neurological disorders Developmental delay Fibroblast culture Nucleotidase assay
This work was supported by local funds of the University of Pisa and the research funds of the University of Siena (PAR 2004, 2005 and 2006). We thank Dr. Tony Marinaki and Dr. Tina Slade of Guy’s Hospital London Great Britain, Dr. Ulrich Frank, Sozialpädiatrisches Zentrum, Braunschweig, Germany, Dr. Gigliola Serra, Istituto di Neuropsichiatria Infantile, Università di Sassari, Italy, for providing fibroblasts of patients and controls.
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