Kinetic characteristics of nucleoside mono-, di- and triphosphatase activities of the periplasmic 5'-nucleotidase of Escherichia coli.

Periplasmic 5'-nucleotidase from Escherichia coli, in addition to the monophosphoesterase activity has a diphosphohydrolase activity, acting on nucleoside di- and triphosphates. We proposed that the monophosphoesterase and diphosphohydrolase activities have their own active site. This proposal is based on the different types of bonds being broken.

Human placental ecto-enzymes: studies on the plasma membrane anchorage and effect of inhibitors of ATP-metabolizing enzymes.

The human placental microvillar membrane contains several ectoenzymes, including 5'-nucleotidase, alkaline phosphatase and ATP-diphosphohydrolase (ATP-DPH), which might be involved in the extracellular metabolism of nucleotides. The type of anchorage to the plasma membrane of the two first enzymes has been shown to be via a glycosyl-phosphatidylinositol. In the present study, using an enzymatic approach, we show that the ATP-DPH should be attached to the plasma membrane through a different type of anchorage.

ATP-diphosphophydrolase activity in rat heart tissue.

Extracellular nucleotides interact with specific receptors on the cell surface and are locally metabolized by ecto-nucleotidases. Biochemical characterization of the ATPase and ADPase activities detected in rat heart sarcolemma, under conditions where mitochondrial ATPase and adenylate kinase were blocked, supports our proposal that both activities correspond to a single enzyme, known as ATP-diphosphohydrolase or apyrase. The physiological function of this enzyme could be dephosphorylation of the nucleotides present in the interstitial heart compartment acting together with 5'-nucleotidase.

Comparison of the biochemical properties, regulation and function of ATP-diphosphohydrolase from human placenta and rat kidney.

ATP-diphosphohydrolase (apyrase. EC 3.6.

ATP-diphosphohydrolase activity in rat renal microvillar membranes and vascular tissue.

Ecto-nucleotidases may have a role in the regulation of purinoceptor-mediated responses. ATP-diphosphohydrolase or apyrase has been described as an ecto-nucleotidase, which is characterized by a low specificity for its substrates and bivalent cations. The aim of this work was to demonstrate the presence of apyrase as an ecto-enzyme in the rat kidney.