Department of Internal Medicine, Laboratory of Biochemistry, The University of Perugia, Via del Giochetto, I-06122, Perugia, Italy.
J Biochem Mol Toxicol. 2012 Mar;26(3):87-93. doi: 10.1002/jbt.21407.
Peroxidases catalyze the oxidation of nitrite to nitrate in the presence of hydrogen peroxide. Two pathways may occur: one entailing the intermediate formation of NO(2) and the other implying the generation of peroxynitrite. The products of nitrite (NO(2) (-) ) oxidation by salivary peroxidase (SPO) and commercial bovine lactoperoxidase (LPO) are studied by utilizing an electrochemical assay that allows the direct, continuous monitoring of NO and/or NO(2) and by HPLC to assess nitrates at the end of the reaction. Dialyzed saliva and LPO, in the presence of H(2) O(2) , convert nitrite into nitrate and form some NO, with a molar ratio of 10(3) . In our experimental conditions, no NO(2) was detectable among the products of nitrite oxidation. SCN(-) inhibits NO formation and so does I(-) , although at higher concentrations. No effects are observed with Cl(-) or Br(-) . We conclude that SPO and LPO transform NO(2) (-) into nitrate-forming small amounts of NO in the presence of H(2) O(2) as an intermediate or a by-product, synthesized through the peroxynitrite pathway.
过氧化物酶在过氧化氢存在的情况下催化亚硝酸盐氧化为硝酸盐。可能发生两种途径：一种需要中间形成 NO(2) ，另一种则暗示过氧亚硝酸盐的生成。利用电化学测定法直接连续监测 NO 和/或 NO(2) ，并在反应结束时通过 HPLC 评估硝酸盐，研究了唾液过氧化物酶 (SPO) 和商业牛乳过氧化物酶 (LPO) 对亚硝酸盐的氧化产物。在 H(2)O(2) 的存在下，透析唾液和 LPO 将亚硝酸盐转化为硝酸盐并形成一些 NO，摩尔比为 10(3) 。在我们的实验条件下，在亚硝酸盐氧化产物中未检测到 NO(2) 。SCN(-) 抑制 NO 的形成，I(-) 也是如此，尽管浓度更高。Cl(-) 或 Br(-) 没有观察到影响。我们得出结论，SPO 和 LPO 在 H(2)O(2) 作为中间产物或副产物存在下将 NO(2) (-) 转化为形成硝酸盐的少量 NO，通过过氧亚硝酸盐途径合成。
