Perry J M, Zhao Y, Marletta M A
Division of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, Michigan 48109-0606, USA.
J Biol Chem. 2000 May 12;275(19):14070-6. doi: 10.1074/jbc.275.19.14070.
Cu(2+) and Zn(2+) inhibit all of the NADPH-dependent reactions catalyzed by neuronal nitric-oxide synthase (nNOS) including ferricytochrome c reduction, NADPH oxidation, and citrulline formation. Cu(2+) and Zn(2+) also inhibit ferricytochrome c reduction by the independent reductase domain. Zn(2+) affects all activities of the full-length nNOS and the reductase domain to the same extent (estimated IC(50) values from 9 to 31 microm), suggesting Zn(2+) occupation of a single site in the reductase domain. Citrulline formation and NADPH oxidation by the full-length nNOS and ferricytochrome c reduction by the reductase domain are affected similarly by Cu(2+), with estimated IC(50) values ranging from 6 to 33 microm. However, Cu(2+) inhibits ferricytochrome c reduction by the full-length nNOS 2 orders of magnitude more potently, with an estimated IC(50) value of 0.12 microm. These data suggest the possibility that Cu(2+) may interact with nNOS at two sites, one composed exclusively of the reductase domain (which is perhaps also involved in Zn(2+)-mediated inhibition), and another that includes components of both domains. Occupation of the second (higher affinity) site could then promote the selective inhibition of ferricytochrome c reduction in full-length nNOS. Neither the inhibition by Cu(2+) nor that by Zn(2+) is dependent on calmodulin.
铜离子（Cu(2+)）和锌离子（Zn(2+)）可抑制神经元型一氧化氮合酶（nNOS）催化的所有依赖烟酰胺腺嘌呤二核苷酸磷酸（NADPH）的反应，包括高铁细胞色素c还原、NADPH氧化和瓜氨酸生成。Cu(2+)和Zn(2+)还可抑制独立还原酶结构域介导的高铁细胞色素c还原。Zn(2+)对全长nNOS和还原酶结构域的所有活性影响程度相同（估计半数抑制浓度（IC(50)）值为9至31微摩尔），这表明Zn(2+)占据了还原酶结构域中的单个位点。全长nNOS催化的瓜氨酸生成和NADPH氧化以及还原酶结构域介导的高铁细胞色素c还原受Cu(2+)的影响相似，估计IC(50)值范围为6至33微摩尔。然而，Cu(2+)抑制全长nNOS介导的高铁细胞色素c还原的效力要强2个数量级，估计IC(50)值为0.12微摩尔。这些数据表明，Cu(2+)可能在两个位点与nNOS相互作用，一个位点仅由还原酶结构域组成（可能也参与Zn(2+)介导的抑制作用），另一个位点包括两个结构域的成分。占据第二个（高亲和力）位点可能会促进对全长nNOS中高铁细胞色素c还原的选择性抑制。Cu(2+)和Zn(2+)的抑制作用均不依赖于钙调蛋白。
