Identification of imidazole as l-arginine-competitive inhibitor of porcine brain nitric oxide synthase |
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Authors: | Bernd Mayer Peter Klatt Ernst R Werner Kurt Schmidt |
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Abstract: | Imidazole acts as a heme-site inhibitor of nitric oxide synthase (NOS). We used this compound to investigate whether the substrate l-arginine binds directly to the heme or to a separate domain of brain NOS. Enzyme kinetic experiments showed that imidazole enhanced the apparent Km for l-arginine without affecting maximal enzyme activity, and binding studies revealed that the inhibitor displaced the radioligand NG-nitro-l-3H]arginine in a concentration-dependent fashion. These results demonstrate that imidazole exerts its effects on NOS in an l-arginine-competitive manner and that the substrate site of the enzyme may be identical with the prosthetic heme group. |
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Keywords: | Nitric oxide synthase Cytochrome P450 Hydrogen peroxide Imidazole Radioligand binding Enzyme kinetics |
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