Structural basis for pterin antagonism in nitric-oxide synthase: Development of novel 4-oxo-pteridine antagonists of (6R)-5,6,7,8-tetrahydrobiopterin

Peter Kotsonis, Lothar G. Fröhlich, C. S. Raman, Huiying Li, Michael Berg, Rainer Gerwig, Viola Groehn, Yonghan Kang, Najim Al-Masoudi, Shahriyar Taghavi-Moghadam, Detlev Mohr, Ursula Münch, Joachim Schnabel, Pavel Martásek, Bettie S.S. Masters, Hartmut Strobel, Thomas Poulos, Hans Matter, Wolfgang Pfleiderer, Harald H.H.W. Schmidt

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Pathological nitric oxide (NO) generation in sepsis, inflammation, and stroke may be therapeutically controlled by inhibiting NO synthases (NOS). Here we targeted the (6R)-5,6,7,8-tetrahydro-L-biopterin (H4Bip)-binding site of NOS, which, upon cofactor binding, maximally increases enzyme activity and NO production from substrate L-arginine. The first generation of H 4Bip-based NOS inhibitors employed a 4-amino pharmacophore of H 4Bip analogous to antifolates such as methotrexate. We developed a novel series of 4-oxo-pteridine derivatives that were screened for inhibition against neuronal NOS (NOS-I) and a structure-activity relationship was determined. To understand the structural basis for pterin antagonism, selected derivatives were docked into the NOS pterin binding cavity. Using a reduced 4-oxo-pteridine scaffold, derivatives with certain modifications such as electron-rich aromatic phenyl or benzoyl groups at the 5- and 6-positions, were discovered to markedly inhibit NOS-I, possibly due to hydrophobic and electrostatic interactions with Phe462 and Ser104, respectively, within the pterin binding pocket. One of the most effective 4-oxo compounds and, for comparisons an active 4-amino derivative, were then co-crystallized with the endothelial NOS (NOS-III) oxygenase domain and this structure solved to confirm the hypothetical binding modes. Collectively, these findings suggest (i) that, unlike the antifolate principle, the 4-amino substituent is not essential for developing pterin-based NOS inhibitors and (ii), provide a steric and electrostatic basis for their rational design.

Original languageEnglish (US)
Pages (from-to)49133-49141
Number of pages9
JournalJournal of Biological Chemistry
Issue number52
StatePublished - Dec 28 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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