Mammalian 5′-Nucleotidases

Nucleoside monophosphate phosphohydrolases or 5′-nucleotidases (members of EC 3.1.3.5 and EC 3.1.3.6) dephosphorylate non-cyclic nucleoside monophosphates to nucleosides and inorganic phosphate. Seven human 5′-nucleotidases with different subcellular localization have been cloned (Table I). Sequence comparisons show high homology only between cytosolic 5′-nucleotidase IA (cN-IA)1 and B and between cytosolic 5′(3′)-deoxynucleotidase (cdN) and mitochondrial 5′(3′)-deoxynucleotidase (mdN). However, the existence of common motifs suggests a common catalytic mechanism for all intracellular 5′-nucleotidases.