Cytoplasmic 5'(3')-nucleotidase from human placenta

J Biol Chem. 1990 Apr 25;265(12):6589-95.


The 5'(3')-nucleotidase earlier partially purified from rat liver by Fritzson and Smith [1971) Biochim. Biophys. Acta 235, 128-141) was purified 15,000-fold to apparent homogeneity from human placenta. The soluble enzyme is a homodimer with a native molecular mass of 44-45 kDa. It has a pH optimum between 6.0 and 6.5 and is absolutely dependent on Mg2+ ions. The enzyme dephosphorylates certain 2'-, 3'-, and 5'-nucleotides. Km values for 2'- and 3'-nucleotides are around 0.3 mM with no preference for either ribo- or deoxyribonucleotides. 5'-Deoxyribonucleotides are 10-fold better substrates than the corresponding ribonucleotides, with dIMP greater than dUMP greater than dGMP greater than dTMP. dAMP is a poor substrate, dCMP is essentially insert. In all cases the Km values are in the millimolar range. Of the different forms of nucleotidases characterized in animal cells, the 5'(3')-nucleotidase is unique in its preference for 5'-deoxyribonucleotides. In intact cells, a portion of de novo synthesized deoxyribonucleotides is degraded as part of a homeostatic mechanism regulating the size of deoxyribonucleotide pools. This requires the participation of one or several 5'-nucleotidases. The 5'(3')-nucleotidase may be one such enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5'-Nucleotidase*
  • Chromatography, Gel
  • Chromatography, Ion Exchange
  • Cytoplasm / enzymology
  • Female
  • Humans
  • Kinetics
  • Macromolecular Substances
  • Molecular Weight
  • Nucleotidases / isolation & purification*
  • Nucleotidases / metabolism
  • Placenta / enzymology*
  • Pregnancy
  • Substrate Specificity


  • Macromolecular Substances
  • 5'(3')-nucleotidase
  • Nucleotidases
  • 5'-Nucleotidase