Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid

Wei Tang, Huiying Li, Emma H. Doud, Yunqiu Chen, Stephanie Choing, Carla Plaza, Neil L. Kelleher*, Thomas L. Poulos, Richard B. Silverman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)5980-5989
Number of pages10
JournalJournal of the American Chemical Society
Issue number18
StatePublished - May 13 2015

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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