Mittal C K
Division of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University, Houston.
Biochem Biophys Res Commun. 1993 May 28;193(1):126-32. doi: 10.1006/bbrc.1993.1599.
The objective of this study was to determine the role of superoxide ion in the formation of nitric oxide by brain NO synthase. NO synthase activity was detected by activation of guanylate cyclase in broken cell preparations. NO synthase activity was dependent on NADPH and was inhibited by EGTA, hemoglobin, Nw-methyl-L-arginine and nitroblue tetrazolium. While the addition of exogenous superoxide dismutase significantly enhanced NO synthase activity, bovine liver catalase completely abolished NO formation. None of these NO synthase modulators, however, altered NO-dependent stimulation of guanylate cyclase activity. These observations indicate that catalytic conversion of L-arginine to nitric oxide by cytosolic, isoform of brain NO synthase requires superoxide ion, hydrogen peroxide and possibly hydroxyl radical.
本研究的目的是确定超氧离子在脑一氧化氮合酶形成一氧化氮过程中的作用。通过破碎细胞制剂中鸟苷酸环化酶的激活来检测一氧化氮合酶活性。一氧化氮合酶活性依赖于NADPH，并受到EGTA、血红蛋白、Nω-甲基-L-精氨酸和氮蓝四唑的抑制。虽然添加外源性超氧化物歧化酶可显著增强一氧化氮合酶活性，但牛肝过氧化氢酶可完全消除一氧化氮的形成。然而，这些一氧化氮合酶调节剂均未改变一氧化氮对鸟苷酸环化酶活性的依赖性刺激。这些观察结果表明，脑一氧化氮合酶胞质同工型将L-精氨酸催化转化为一氧化氮需要超氧离子、过氧化氢以及可能的羟基自由基。
