Brunelli L, Yermilov V, Beckman J S
Division of Neonatal Medicine, Duke University Medical Center, Durham, NC, USA.
Free Radic Biol Med. 2001 Apr 1;30(7):709-14. doi: 10.1016/s0891-5849(00)00512-8.
Previously, we found that catalase enhanced the protection afforded by superoxide dismutase to Escherichia coli against the simultaneous generation of superoxide and nitric oxide (Brunelli et al., Arch. Biochem. Biophys. 316:327-334, 1995). Hydrogen peroxide itself was not toxic in this system in the presence or absence of superoxide dismutase. We therefore investigated whether catalase might consume nitric oxide in addition to hydrogen peroxide. Catalase rapidly formed a reversible complex stoichiometrically with nitric oxide with the Soret band shifting from 406 to 426 nm and two new peaks appeared at 540 and at 575 nm, consistent with the formation of a ferrous-nitrosyl complex. Catalase consumed more nitric oxide upon the addition of hydrogen peroxide. Conversely, micromolar concentrations of nitric oxide slowed the catalase-mediated decomposition of hydrogen peroxide. Catalase pretreated with nitric oxide and hydrogen peroxide regained full activity after dialysis. Our results suggest that catalase can slowly consume nitric oxide while nitric oxide modestly inhibits catalase-dependent scavenging of hydrogen peroxide. The protective effects of catalase in combination with superoxide dismutase may result from two actions; reducing peroxynitrite formation by scavenging nitric oxide and by scavenging hydrogen peroxide before it reacts with superoxide dismutase to form additional superoxide.
此前，我们发现过氧化氢酶增强了超氧化物歧化酶对大肠杆菌的保护作用，使其免受超氧化物和一氧化氮的同时产生的影响（布鲁内利等人，《生物化学与生物物理学报》316:327 - 334，1995年）。在有或没有超氧化物歧化酶的情况下，过氧化氢本身在该系统中并无毒性。因此，我们研究了过氧化氢酶除了消耗过氧化氢外是否还可能消耗一氧化氮。过氧化氢酶与一氧化氮迅速形成化学计量的可逆复合物，索雷特带从406纳米移至426纳米，并且在540纳米和575纳米处出现两个新峰，这与亚铁 - 亚硝酰复合物的形成一致。加入过氧化氢后，过氧化氢酶消耗了更多的一氧化氮。相反，微摩尔浓度的一氧化氮减缓了过氧化氢酶介导的过氧化氢分解。用一氧化氮和过氧化氢预处理的过氧化氢酶在透析后恢复了全部活性。我们的结果表明，过氧化氢酶可以缓慢消耗一氧化氮，而一氧化氮适度抑制过氧化氢酶对过氧化氢的清除。过氧化氢酶与超氧化物歧化酶联合使用的保护作用可能源于两种作用；通过清除一氧化氮以及在过氧化氢与超氧化物歧化酶反应形成额外的超氧化物之前清除过氧化氢来减少过氧亚硝酸盐的形成。
