Ecto-5-prime-nucleotidase (5-prime-ribonucleotide phosphohydrolase) catalyzes the conversion at neutral pH of purine 5-prime mononucleotides to nucleosides, the preferred substrate being AMP. The enzyme consists of a dimer of 2 identical 70 kD subunits bound externally to the plasma membrane by a glycosyl phosphatidyl inositol linkage. The enzyme is used as a marker of lymphocyte differentiation. Consequently, a deficiency of NT5E occurs in a variety of immunodeficiency diseases. Other forms of 5-prime nucleotidase exist in the cytoplasm and lysosomes and can be distinguished from ecto-NT5 by their substrate affinities, requirement for divalent magnesium ion, activation by ATP, and inhibition by inorganic phosphate. It is not known whether the different enzymes are coded by different genes or result from different posttranslational modifications of a single coding sequence.

HUMAN

2-8°C (short-term); -20°C (long-term)