Conformationally-restricted arginine analogues as alternative substrates and inhibitors of nitric oxide synthases.
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.
Lee
Y
Y
Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
Marletta
M A
MA
Martasek
P
P
Roman
L J
LJ
Masters
B S
BS
Silverman
R B
RB
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
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D001120:Arginine; D019001:Nitric Oxide Synthase