title: Structural basis for pterin antagonism in nitric-oxide synthase. Development of novel 4-oxo-pteridine antagonists of (6R)-5,6,7,8-tetrahydrobiopterin.
abstract: 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 (H(4)Bip)-binding site of NOS, which, upon cofactor binding, maximally increases enzyme activity and NO production from substrate l-arginine. The first generation of H(4)Bip-based NOS inhibitors employed a 4-amino pharmacophore of H(4)Bip 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 Phe(462) and Ser(104), 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.
authors.affiliation: Department of Pharmacology and Toxicology, Julius-Maximilians University, Versbacher Strasse 9, Würzburg 97078, Germany. peter.kotsonis@pharma.novartis.com
authors.forename: P
authors.initials: P
authors.lastname: Kotsonis
authors.forename: L G
authors.initials: LG
authors.lastname: Fröhlich
authors.forename: C S
authors.initials: CS
authors.lastname: Raman
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Berg
authors.forename: R
authors.initials: R
authors.lastname: Gerwig
authors.forename: V
authors.initials: V
authors.lastname: Groehn
authors.forename: Y
authors.initials: Y
authors.lastname: Kang
authors.forename: N
authors.initials: N
authors.lastname: Al-Masoudi
authors.forename: S
authors.initials: S
authors.lastname: Taghavi-Moghadam
authors.forename: D
authors.initials: D
authors.lastname: Mohr
authors.forename: U
authors.initials: U
authors.lastname: Münch
authors.forename: J
authors.initials: J
authors.lastname: Schnabel
authors.forename: P
authors.initials: P
authors.lastname: Martásek
authors.forename: B S
authors.initials: BS
authors.lastname: Masters
authors.forename: H
authors.initials: H
authors.lastname: Strobel
authors.forename: T
authors.initials: T
authors.lastname: Poulos
authors.forename: H
authors.initials: H
authors.lastname: Matter
authors.forename: W
authors.initials: W
authors.lastname: Pfleiderer
authors.forename: H H
authors.initials: HH
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D001708:Biopterins / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism*; D002531:Cerebellum / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D000975:Antioxidants; D007527:Isoenzymes; D001708:Biopterins; D019001:Nitric Oxide Synthase; C003402:sapropterin