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Publication Abstract from PubMed

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 obtained, and their crystal structures determined. The identification and characterization of 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.

Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic acid.,Tang W, Li H, Doud EH, Chen Y, Choing S, Plaza C, Kelleher NL, Poulos TL, Silverman RB J Am Chem Soc. 2015 Apr 15. PMID:25874809^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.