Nitrocatechols versus nitrocatecholamines as novel competitive inhibitors of neuronal nitric oxide synthase: lack of the aminoethyl side chain determines loss of tetrahydrobiopterin-antagonizing properties.

6-Nitrocatecholamines were recently described as novel neuronal nitric oxide synthase inhibitors competing with both L-arginine and tetrahydrobiopterin (BH4). We report now that simple nitrocatechols are also competitive inhibitors, lacking however BH4-antagonizing properties. It is argued that 6-nitrocatecholamines interact with the L-arginine- and BH4-binding sites through the nitrocatechol and aminoethyl moieties, respectively.