title: Conformationally-restricted arginine analogues as alternative substrates and inhibitors of nitric oxide synthases.
abstract: Conformationally restricted arginine analogues (1-5) were synthesized and found to be alternative substrates or inhibitors of the three isozymes of nitric oxide synthase (NOS). A comparison of k(cat)/Km values shows that (E)-3,4-didehydro-D,L-arginine (1) is a much better substrate than the corresponding (Z)-isomer (2) and 3-guanidino-D,L-phenylglycine (3), although none is as good a substrate as is arginine; 5-keto-D,L-arginine (4) is not a substrate, but is an inhibitor of the three isozymes. Therefore, it appears that arginine binds to all of the NOS isozymes in an extended (E-like) conformation. None of the compounds exhibits time-dependent inhibition of NOS, but they are competitive reversible inhibitors. Based on the earlier report that N(omega)-propyl-L-arginine is a highly selective nNOS inhibitor (Zhang, H. Q.; Fast, W.; Marletta, M.; Martasek, P.; Silverman, R. B. J. Med. Chem. 1997, 40, 3869), (E)-N(omega)-propyl-3,4-didehydro-D,L-arginine (5) was synthesized, but it was shown to be weakly potent and only a mildly selective inhibitor of NOS. Imposing conformational rigidity on an arginine backbone does not appear to be a favorable approach for selective NOS inhibition.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Lee
authors.forename: M A
authors.initials: MA
authors.lastname: Marletta
authors.forename: P
authors.initials: P
authors.lastname: Martasek
authors.forename: L J
authors.initials: LJ
authors.lastname: Roman
authors.forename: B S
authors.initials: BS
authors.lastname: Masters
authors.forename: R B
authors.initials: RB
authors.lastname: Silverman
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D015394:Molecular Structure; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D001120:Arginine; D019001:Nitric Oxide Synthase