The effect of divalent cations on neuronal nitric oxide synthase activity.
Neuronal nitric oxide synthase (NOS I) is a Ca(2+)/calmodulin-binding enzyme that generates nitric oxide (NO*) and L-citrulline from the oxidation of L-arginine, and superoxide (O(2)*(-)) from the one-electron reduction of oxygen (O(2)). Nitric oxide in particular has been implicated in many physiological processes, including vasodilator tone, hypertension, and the development and properties of neuronal function. Unlike Ca(2+), which is tightly regulated in the cell, many other divalent cations are unfettered and can compete for the four Ca(2+) binding sites on calmodulin. The results presented in this article survey the effects of various divalent metal ions on NOS I-mediated catalysis. As in the case of Ca(2+), we demonstrate that Ni(2+), Ba(2+), and Mn(2+) can activate NOS I to metabolize L-arginine to L-citrulline and NO*, and afford O(2)*(-) in the absence of L-arginine. In contrast, Cd(2+) did not activate NOS I to produce either NO* or O(2)*(-), and the combination of Ca(2+) and either Cd(2+), Ni(2+), or Mn(2+) inhibited enzyme activity. These interactions may initiate cellular toxicity by negatively affecting NOS I activity through production of NO*, O(2)*(-) and products derived from these free radicals.
Weaver
John
J
Department of Chemistry, University of Maryland Baltimore County, Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Center for Low Frequency EPR for In Vivo Physiology, Baltimore, Maryland, USA. weaver@gl.umbc.edu
Porasuphatana
Supatra
S
Tsai
Pei
P
Cao
Guan-Liang
GL
Budzichowski
Theodore A
TA
Roman
Linda J
LJ
Rosen
Gerald M
GM
D001120:Arginine / Q000378:metabolism; D001464:Barium / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism; D002413:Cations, Divalent / Q000494:pharmacology*; D002956:Citrulline / Q000378:metabolism; D003497:Cyclic N-Oxides; D045304:Cytochromes c / Q000378:metabolism; D007202:Indicators and Reagents; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000302:isolation & purification / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D017382:Reactive Oxygen Species / Q000633:toxicity; D019097:Spin Trapping; D014969:Xanthine Oxidase / Q000378:metabolism
D002147:Calmodulin; D002413:Cations, Divalent; D003497:Cyclic N-Oxides; D007202:Indicators and Reagents; D017382:Reactive Oxygen Species; D002104:Cadmium; C050696:5-butyl-5-methyl-1-pyrroline 1-oxide; D001464:Barium; D002956:Citrulline; D009569:Nitric Oxide; D008345:Manganese; D009532:Nickel; D045304:Cytochromes c; D001120:Arginine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D014969:Xanthine Oxidase