title: Substrate-Dependence of Competitive Nucleotide Pyrophosphatase/Phosphodiesterase1 (NPP1) Inhibitors.
abstract: Nucleotide pyrophosphatase/phosphodiesterase type 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its major substrate is ATP which is converted to AMP and diphosphate. NPP1 was proposed as a new therapeutic target in brain cancer and immuno-oncology. Several NPP1 inhibitors have been reported to date, most of which were evaluated vs. the artificial substratep-nitrophenyl 5'-thymidine monophosphate (p-Nph-5'-TMP). Recently, we observed large discrepancies in inhibitory potencies for a class of competitive NPP1 inhibitors when tested vs. the artificial substratep-Nph-5'-TMP as compared to the natural substrate ATP. Therefore, the goal of the present study was to investigate whether inhibitors of human NPP1 generally display substrate-dependent inhibitory potency. Systematic evaluation of nucleotidic as well as non-nucleotidic NPP1 inhibitors revealed significant differences in determinedKivalues for competitive, but not for non- and un-competitive inhibitors when tested vs. the frequently used artificial substratep-Nph-5'-TMP as compared to ATP. Allosteric modulation of NPP1 byp-Nph-5'-TMP may explain these discrepancies. Results obtained using the AMP derivativep-nitrophenyl 5'-adenosine monophosphate (p-Nph-5'-AMP) as an alternative artificial substrate correlated much better with those employing the natural substrate ATP.
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Sang-Yong
authors.initials: SY
authors.lastname: Lee
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Soumya
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Bhattarai
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Vigneshwaran
authors.initials: V
authors.lastname: Namasivayam
authors.affiliation: Laboratory of Medicinal Chemistry, KU Leuven, Rega Institute for Medical Research Leuven, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: De Jonghe
authors.affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Dresden, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Stephan
authors.affiliation: Laboratory of Medicinal Chemistry, KU Leuven, Rega Institute for Medical Research Leuven, Belgium.
authors.forename: Piet
authors.initials: P
authors.lastname: Herdewijn
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Ali
authors.initials: A
authors.lastname: El-Tayeb
authors.affiliation: PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn Bonn, Germany.
authors.forename: Christa E
authors.initials: CE
authors.lastname: Müller
keywords: NPP1; NPP1 inhibitors; ectonucleotidase inhibitors; enzyme assay; nucleotide pyrophosphatase 1; p-nitrophenyl 5′-thymidine monophosphate