Ogawa Takuro, Furusawa Toshinari, Shiga Michiko, Seo Daisuke, Sakurai Hidehiro, Inoue Kazuhito
Graduate School of Science, University of Tokyo, Japan.
Biosci Biotechnol Biochem. 2010;74(4):771-80. doi: 10.1271/bbb.90815. Epub 2010 Apr 7.
In the green sulfur bacterium Chlorobaculum tepidum, three sulfur oxidizing enzyme system (Sox) proteins, SoxAXK, SoxYZ, and SoxB (the core TOMES, thiosulfate oxidizing multi-enzyme system) are essential to in vitro thiosulfate oxidation. We purified monomeric flavoprotein SoxF from this bacterium, which had sulfide dehydrogenase activity. SoxF enhanced the thiosulfate oxidation activity of the purified core TOMES with various cytochromes as electron acceptors to different degrees without any change in the affinity for thiosulfate. The apparent reaction rates with 50 microM- C. tepidum cytochrome c-554 were slightly higher than with horse-heart cytochrome c, and the addition of 0.5 microM- SoxF increased the rate by 92%. The rates with 50 microM- horse-heart cytochrome c and 50 muM- horse-heart cytochrome c plus 0.5 muM- cytochrome c-554 were increased by SoxF by 31% and 120% respectively. We conclude that SoxF mediates electron transfer between the components of core TOMES and externally added cytochromes.
在绿色硫细菌嗜温绿菌（Chlorobaculum tepidum）中，三种硫氧化酶系统（Sox）蛋白，即SoxAXK、SoxYZ和SoxB（核心TOMES，硫代硫酸盐氧化多酶系统）对于体外硫代硫酸盐氧化至关重要。我们从这种细菌中纯化出了具有硫化物脱氢酶活性的单体黄素蛋白SoxF。SoxF以各种细胞色素作为电子受体，不同程度地增强了纯化后的核心TOMES的硫代硫酸盐氧化活性，而对硫代硫酸盐的亲和力没有任何变化。与50微摩尔的嗜温绿菌细胞色素c-554反应的表观速率略高于与马心细胞色素c反应的速率，添加0.5微摩尔的SoxF可使速率提高92%。SoxF使与50微摩尔马心细胞色素c以及50微摩尔马心细胞色素c加0.5微摩尔细胞色素c-554反应的速率分别提高了31%和120%。我们得出结论，SoxF介导了核心TOMES各组分与外部添加的细胞色素之间的电子转移。
