title: Nitric oxide inhibits ornithine decarboxylase via S-nitrosylation of cysteine 360 in the active site of the enzyme.
abstract: Ornithine decarboxylase is the initial and rate-limiting enzyme in the polyamine biosynthetic pathway. Polyamines are found in all mammalian cells and are required for cell growth. We previously demonstrated that N-hydroxyarginine and nitric oxide inhibit tumor cell proliferation by inhibiting arginase and ornithine decarboxylase, respectively, and, therefore, polyamine synthesis. In addition, we showed that nitric oxide inhibits purified ornithine decarboxylase by S-nitrosylation. Herein we provide evidence for the chemical mechanism by which nitric oxide and S-nitrosothiols react with cysteine residues in ornithine decarboxylase to form an S-nitrosothiol(s) on the protein. The diazeniumdiolate nitric oxide donor agent 1-diethyl-2-hydroxy-2-nitroso-hydrazine acts through an oxygen-dependent mechanism leading to formation of the nitrosating agents N(2)O(3) and/or N(2)O(4). S-Nitrosoglutathione inhibits ornithine decarboxylase by an oxygen-independent mechanism likely by S-transnitrosation. In addition, we provide evidence for the S-nitrosylation of 4 cysteine residues per ornithine decarboxylase monomer including cysteine 360, which is critical for enzyme activity. Finally S-nitrosylated ornithine decarboxylase was isolated from intact cells treated with nitric oxide, suggesting that nitric oxide may regulate ornithine decarboxylase activity by S-nitrosylation in vivo.
authors.affiliation: Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, California 90095-1735, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Bauer
authors.forename: G M
authors.initials: GM
authors.lastname: Buga
authors.forename: J M
authors.initials: JM
authors.lastname: Fukuto
authors.forename: A E
authors.initials: AE
authors.lastname: Pegg
authors.forename: L J
authors.initials: LJ
authors.lastname: Ignarro
mesh_terms: D001665:Binding Sites; D003497:Cyclic N-Oxides / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008163:Luminescent Measurements; D009569:Nitric Oxide / Q000502:physiology*; D009589:Nitrogen Oxides; D009603:Nitroso Compounds / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000737:chemistry / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D010782:Photolysis; D026422:S-Nitrosoglutathione
chemical_list: D003497:Cyclic N-Oxides; D006834:Hydrazines; D007093:Imidazoles; D009589:Nitrogen Oxides; D009603:Nitroso Compounds; D065108:Ornithine Decarboxylase Inhibitors; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; D009955:Ornithine Decarboxylase; D005978:Glutathione; D003545:Cysteine