Lesuisse E, Casteras-Simon M, Labbe P
Laboratoire de Biochimie des Porphyrines, Institut Jacques Monod, Tour 43, Université Paris 7, 2 Place Jussieu, 75251 Paris Cedex 05, France.
J Biol Chem. 1996 Jun 7;271(23):13578-83. doi: 10.1074/jbc.271.23.13578.
We have studied the relationships between in vivo (whole cells) and in vitro (plasma membranes) ferrireductase activity in Saccharomyces cerevisiae. Isolated plasma membranes were enriched in the product of the FRE1 gene and had NADPH dehydrogenase activity that was increased when the cells were grown in iron/copper-deprived medium. The diaphorase activity was, however, independent of Fre1p, and Fre1p itself had no ferrireductase activity in vitro. There were striking similarities between the yeast ferrireductase system and the neutrophil NADPH oxidase: oxygen could act as an electron acceptor in the ferrireductase system, and Fre1p, like gp91, is a glycosylated hemoprotein with a b-type cytochrome spectrum. The ferrireductase system was sensitive to the NADPH oxidase inhibitor diphenylene iodonium (DPI). DPI inhibition proceeded with two apparent Ki values (high and low affinity binding) in whole wild-type and Deltafre2 cells and with one apparent Ki in Deltafre1 cells (high affinity binding) and in plasma membranes (low affinity binding). These results suggest that the Fre1-dependent ferrireductase system involves at least two components (Fre1p and an NADPH dehydrogenase component) differing in their sensitivities to DPI, as in the neutrophil NADPH oxidase. A third component, the product of the UTR1 gene, was shown to act synergistically with Fre1p to increase the cell ferrireductase activity.
我们研究了酿酒酵母体内（全细胞）和体外（质膜）铁还原酶活性之间的关系。分离的质膜富含FRE1基因的产物，并且具有NADPH脱氢酶活性，当细胞在缺铁/铜的培养基中生长时该活性会增加。然而，黄递酶活性不依赖于Fre1p，并且Fre1p本身在体外没有铁还原酶活性。酵母铁还原酶系统与中性粒细胞NADPH氧化酶之间存在显著相似之处：在铁还原酶系统中氧气可作为电子受体，并且Fre1p与gp91一样，是一种具有b型细胞色素光谱的糖基化血红蛋白。铁还原酶系统对NADPH氧化酶抑制剂二亚苯基碘鎓（DPI）敏感。在野生型和Δfre2全细胞中，DPI抑制呈现两个明显的Ki值（高亲和力结合和低亲和力结合），而在Δfre1细胞（高亲和力结合）和质膜（低亲和力结合）中呈现一个明显的Ki值。这些结果表明，依赖于Fre1的铁还原酶系统至少涉及两个对DPI敏感性不同的组分（Fre1p和一个NADPH脱氢酶组分），如同在中性粒细胞NADPH氧化酶中一样。第三个组分，UTR1基因的产物，被证明与Fre1p协同作用以增加细胞铁还原酶活性。
