Riedel H D, Remus A J, Fitscher B A, Stremmel W
Department of Medicine, University Hospital of Heidelberg, Germany.
Biochem J. 1995 Aug 1;309 ( Pt 3)(Pt 3):745-8. doi: 10.1042/bj3090745.
Reduction of ferric iron in the presence of HuTu 80 cells or duodenal microvillus membranes (MVMs) was investigated. With both systems, NADH-dependent reduction of Fe3+/NTA (nitrilotriacetic acid) was demonstrated, using the ferrous iron chelator ferrozine. Uptake of Fe3+ from Fe3+/NTA by HuTu 80 cells was strongly inhibited by addition of ferrozine, indicating that Fe2+ is the substrate for the iron uptake system. With isolated plasma membranes it is shown that the reductase activity is sensitive to trypsin and incubation at 65 degrees C. The reductase activity could be extracted from the plasma membrane and partially purified by ammonium sulphate precipitation and isoelectric focusing. From the purification and inhibition characteristics we conclude that reduction of ferric iron on the surface of duodenal plasma membranes is catalysed by a membrane protein.
研究了在胡图80细胞或十二指肠微绒毛膜（MVM）存在下三价铁的还原情况。在这两种体系中，使用亚铁螯合剂菲咯嗪证明了NADH依赖的Fe3+/NTA（次氮基三乙酸）还原反应。加入菲咯嗪后，胡图80细胞从Fe3+/NTA摄取Fe3+的过程受到强烈抑制，这表明Fe2+是铁摄取系统的底物。对于分离的质膜，结果显示还原酶活性对胰蛋白酶和65℃孵育敏感。还原酶活性可从质膜中提取出来，并通过硫酸铵沉淀和等电聚焦进行部分纯化。根据纯化和抑制特性，我们得出结论，十二指肠质膜表面三价铁的还原是由一种膜蛋白催化的。
