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首页> 外文期刊>Biochemical and Biophysical Research Communications >Flavohemoglobin and nitric oxide detoxification in the human protozoan parasite Giardia intestinalis.
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Flavohemoglobin and nitric oxide detoxification in the human protozoan parasite Giardia intestinalis.

机译：在人类原生动物寄生虫贾第虫肠中的黄素血红蛋白和一氧化氮排毒。

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摘要

Flavohemoglobins (flavoHbs), commonly found in bacteria and fungi, afford protection from nitrosative stress by degrading nitric oxide (NO) to nitrate. Giardia intestinalis, a microaerophilic parasite causing one of the most common intestinal human infectious diseases worldwide, is the only pathogenic protozoon as yet identified coding for a flavoHb. By NO amperometry we show that, in the presence of NADH, the recombinant Giardia flavoHb metabolizes NO with high efficacy under aerobic conditions (TN=116+/-10s(-1) at 1microM NO, T=37 degrees C). The activity is [O(2)]-dependent and characterized by an apparent K(M,O2)=22+/-7microM. Immunoblotting analysis shows that the protein is expressed at low levels in the vegetative trophozoites of Giardia; accordingly, these cells aerobically metabolize NO with low efficacy. Interestingly, in response to nitrosative stress (24-h incubation with 5mM nitrite) flavoHb expression is enhanced and the trophozoites thereby become able to metabolize NO efficiently, the activity being sensitive to both cyanide and carbon monoxide. The NO-donors S-nitrosoglutathione (GSNO) and DETA-NONOate mimicked the effect of nitrite on flavoHb expression. We propose that physiologically flavoHb contributes to NO detoxification in G. intestinalis.
机译：常存在于细菌和真菌中的黄素血球蛋白（flavoHbs）通过将一氧化氮（NO）降解为硝酸盐而提供保护，使其免受亚硝化胁迫。贾第鞭毛虫是引起全球人类最常见的肠道传染病之一的微需氧寄生虫，是唯一已确定编码flavoHb的致病性原生动物。通过NO安培法，我们显示出在NADH存在下，重组贾第鞭毛虫flavoHb在有氧条件下（TN = 116 +/- 10s（-1）在1microM NO，T = 37摄氏度）下高效代谢NO。活性是[O（2）]依赖性的，其特征在于表观K（M，O2）= 22 +/- 7microM。免疫印迹分析表明该蛋白在贾第鞭毛虫的营养滋养体中低水平表达。因此，这些细胞需氧代谢的NO效率低。有趣的是，响应亚硝化胁迫（与5mM亚硝酸盐孵育24小时），flavoHb的表达增强，滋养体因此变得能够有效代谢NO，该活性对氰化物和一氧化碳均敏感。 NO供体S-亚硝基谷胱甘肽（GSNO）和DETA-NONOate模仿了亚硝酸盐对flavoHb表达的影响。我们建议生理上flavoHb有助于肠球菌的NO解毒。

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