title: Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid.
abstract: Nitric oxide synthase (NOS) catalyzes the conversion of l-arginine to l-citrulline and the second messenger nitric oxide. Three mechanistic pathways are proposed for the inactivation of neuronal NOS (nNOS) by (S)-2-amino-5-(2-(methylthio)acetimidamido)pentanoic acid (1): sulfide oxidation, oxidative dethiolation, and oxidative demethylation. Four possible intermediates were synthesized. All compounds were assayed with nNOS, their IC50, KI, and kinact values were obtained, and their crystal structures were determined. The identification and characterization of the products formed during inactivation provide evidence for the details of the inactivation mechanism. On the basis of these studies, the most probable mechanism for the inactivation of nNOS involves oxidative demethylation with the resulting thiol coordinating to the cofactor heme iron. Although nNOS is a heme-containing enzyme, this is the first example of a NOS that catalyzes an S-demethylation reaction; the novel mechanism of inactivation described here could be applied to the design of inactivators of other heme-dependent enzymes.
authors: †Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Wei
authors: W
authors: Tang
authors: ‡Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States.
authors: Huiying
authors: H
authors: Li
authors: §Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Emma H
authors: EH
authors: Doud
authors: §Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Yunqiu
authors: Y
authors: Chen
authors: †Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Stephanie
authors: S
authors: Choing
authors: ‡Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States.
authors: Carla
authors: C
authors: Plaza
authors: §Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Neil L
authors: NL
authors: Kelleher
authors: ‡Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States.
authors: Thomas L
authors: TL
authors: Poulos
authors: †Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors: Richard B
authors: RB
authors: Silverman
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects*; D005557:Formaldehyde / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D010421:Pentanoic Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: C000604590:(S)-2-amino-5-(2-(methylthio)acetimidamido)pentanoic acid; D000596:Amino Acids; D010421:Pentanoic Acids; D005557:Formaldehyde; D052248:Nitric Oxide Synthase Type I