Hashimoto Muneaki, Takamiya Shinzaburo, Yokota Takehiro, Nakajima Yoshitaka, Yamakura Fumiyuki, Sugio Shigetoshi, Aoki Takashi
Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
Arch Biochem Biophys. 2008 Mar 1;471(1):42-9. doi: 10.1016/j.abb.2007.12.003. Epub 2007 Dec 15.
The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, thus co-localizing with Ascaris hemoglobin. We also found that cytochrome b5 reduces Ascaris non-functioning ferric methemoglobin more efficiently than mammalian methemoglobin. Furthermore, a computer graphics model of the electron transfer complex between Ascaris cytochrome b5 and Ascaris hemoglobin strongly suggested that these two proteins are physiological redox partners. Nitric oxide has been reported to react easily with oxygen captured in hemoglobin to form nitrate, but not toxic free radicals, which may result in production of methemoglobin for the cytochrome b5 to regenerate functional ferrous hemoglobin. Therefore, our findings suggest that Ascaris cytochrome b5 is a key redox partner of Ascaris hemoglobin, which acts as an antioxidant.
厌氧寄生线虫猪蛔虫在围脏液中有一种对氧有高度亲和力的血红蛋白，其生物学功能仍不清楚。在此，我们报告猪蛔虫细胞色素b5在肠道寄生阶段特异性表达，并分泌到围脏液中，从而与猪蛔虫血红蛋白共定位。我们还发现，细胞色素b5比哺乳动物的高铁血红蛋白更有效地还原猪蛔虫无功能的高铁血红蛋白。此外，猪蛔虫细胞色素b5与猪蛔虫血红蛋白之间电子传递复合物的计算机图形模型强烈表明，这两种蛋白质是生理氧化还原伙伴。据报道，一氧化氮很容易与血红蛋白中捕获的氧反应形成硝酸盐，而不是有毒的自由基，这可能导致高铁血红蛋白的产生，供细胞色素b5再生功能性亚铁血红蛋白。因此，我们的研究结果表明，猪蛔虫细胞色素b5是猪蛔虫血红蛋白的关键氧化还原伙伴，后者起到抗氧化剂的作用。
