Ca2+ or Mg2+ nucleotide phosphohydrolases in myometrium

two ecto-enzymes

M. Magócsi, John T. Penniston

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

A high level of Ca2+ or Mg2+ nucleotide phosphodydrolase activity is present on the outside surface of intact myometrial cells and is also observed in the isolated plasma membranes. About half of this activity is labile while the remainder is stable. The characteristics of the activities suggest the presence of at least two different ecto-enzymes. The stable component (Km for Ca2+ about 0.1 mM)_accepts XTP or XDP as substrate, is not inhibited by p-chloromercuriphenylsulfonate or inorganic phosphate, but is inhibited by 20 mM NaN3. The labile component (Km for Ca2+ nearly 1 mM) cleaves XTP but not XDP, and is inhibited by p-chloromercuriphenyl-sulfonate and inorganic phosphate, but not by NaN3. The activity of the labile component can be restored by removing the cells from the incubation medium and resuspending them in fresh medium. This suggests that the 'lability' is due to product inhibition, probably by inorganic orthophosphate. While the Ca2+ pump of myometrial plasma membranes was inhibited by 0.1 μM oxytocin, these ecto-enzymes were unaffected by oxytocin concentrations up to 10 μM. Because of its high activity and rapid inactivation by product inhibition, the labile enzyme may be involved in the regulation of purinergic receptors.

Original languageEnglish
Pages (from-to)163-172
Number of pages10
JournalBBA - Biomembranes
Volume1070
Issue number1
DOIs
Publication statusPublished - Nov 18 1991

Fingerprint

nucleotidase
Myometrium
Sodium Azide
Phosphates
Oxytocin
Cell membranes
4-Chloromercuribenzenesulfonate
Enzymes
Cell Membrane
Purinergic Receptors
Byproducts
Nucleotides
Pumps
Substrates

Keywords

  • ATP diphosphohydrolase
  • ATPase
  • ATPase, (Ca + Mg)-, nonspecific
  • Ectoenzyme
  • Myometrium
  • Plasma membrane

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology
  • Medicine(all)

Cite this

Ca2+ or Mg2+ nucleotide phosphohydrolases in myometrium : two ecto-enzymes. / Magócsi, M.; Penniston, John T.

In: BBA - Biomembranes, Vol. 1070, No. 1, 18.11.1991, p. 163-172.

Research output: Contribution to journalArticle

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