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cytosolic 5'-nucleotidase II (cN-II) similar to human NT5DC1 (5'-nucleotidase domain-containing protein 1) and NT5DC2 Cytosolic 5'-nucleotidase II (cN-II), also known as purine 5'-nucleotidase, IMP-GMP specific nucleotidase, or high Km 5prime-nucleotidase, catalyzes the dephosphorylation of 6-hydroxypurine nucleoside monophosphates. It is ubiquitously expressed and likely to play an important role in the regulation of purine nucleotide interconversions and in the regulation of IMP and GMP pools within the cell. It is also acts as a phosphotransferase, catalyzing the reverse reaction, the transfer of a phosphate from a monophosphate substrate to a nucleoside acceptor, to form a nucleoside monophosphate. The nucleoside acceptor is preferentially inosine and deoxyinosine, phosphate donors include any 6-hydroxypurine monophosphate substrate of the nucleotidase reaction. Both the dephosphorylation and phosphotransferase reactions are allosterically activated by adenine-based nucleotides and 2,3-bisphosphoglycerate. Members of this family belong to the haloacid dehalogenase-like (HAD) hydrolases, a large superfamily of diverse enzymes that catalyze carbon or phosphoryl group transfer reactions on a range of substrates, using an active site aspartate in nucleophilic catalysis. Members of this superfamily include 2-L-haloalkanoic acid dehalogenase, azetidine hydrolase, phosphonoacetaldehyde hydrolase, phosphoserine phosphatase, phosphomannomutase, P-type ATPases and many others. HAD hydrolases are found in all three kingdoms of life, and most genomes are predicted to contain multiple HAD-like proteins. Members possess a highly conserved alpha/beta core domain, and many also possess a small cap domain, the fold and function of which is variable. HAD hydrolases are sometimes referred to as belonging to the DDDD superfamily of phosphohydrolases.
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