Hyman M R, Arp D J
Department of Biochemistry, University of California, Riverside.
Biochim Biophys Acta. 1991 Jan 29;1076(2):165-72. doi: 10.1016/0167-4838(91)90261-w.
The effects of nitric oxide (NO) on the membrane-associated form of the nickel and iron-sulfur-containing hydrogenase from Azotobacter vinelandii have been investigated. In the presence of H2 and an electron acceptor (turnover conditions), NO acts as a noncompetitive inhibitor vs. methylene blue (Ki = 12 microM). There is no element of competition between NO and H2, implying that the site of NO action is not the H2-activating site of the hydrogenase. When the membrane-associated hydrogenase is incubated under non-turnover conditions, the enzyme is irreversibly inactivated by NO in a time-dependent process. The inactivation is a non-saturable, pseudo-first-order process which is consistent with a direct chemical reaction between NO and the hydrogenase. Kinetic evidence is presented which is compatible with an interaction between NO and a redox-active component other than the H2-activating site on the enzyme. The complex inhibition pattern of NO has been interpreted in terms of two distinct interactions of NO with iron-sulfur centers of the hydrogenase.
研究了一氧化氮（NO）对来自棕色固氮菌的与膜相关的含镍和铁硫氢化酶形式的影响。在H2和电子受体存在的情况下（周转条件），相对于亚甲基蓝，NO作为非竞争性抑制剂（Ki = 12 microM）。NO和H2之间不存在竞争因素，这意味着NO的作用位点不是氢化酶的H2激活位点。当膜相关氢化酶在非周转条件下孵育时，该酶会被NO以时间依赖性过程不可逆地失活。失活是一个非饱和的伪一级过程，这与NO和氢化酶之间的直接化学反应一致。给出的动力学证据与NO和酶上H2激活位点以外的氧化还原活性成分之间的相互作用相符。NO的复杂抑制模式已根据NO与氢化酶铁硫中心的两种不同相互作用进行了解释。
