Center for Biomedical Engineering NE47-379, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA.
Proc Natl Acad Sci U S A. 2011 Jun 7;108(23):9396-401. doi: 10.1073/pnas.1103659108. Epub 2011 May 23.
Photosynthetic water splitting, coupled to hydrogenase-catalyzed hydrogen production, is considered a promising clean, renewable source of energy. It is widely accepted that the oxygen sensitivity of hydrogen production, combined with competition between hydrogenases and NADPH-dependent carbon dioxide fixation are the main limitations for its commercialization. Here we provide evidence that, under the anaerobic conditions that support hydrogen production, there is a significant loss of photosynthetic electrons toward NADPH production in vitro. To elucidate the basis for competition, we bioengineered a ferredoxin-hydrogenase fusion and characterized hydrogen production kinetics in the presence of Fd, ferredoxin:NADP(+)-oxidoreductase (FNR), and NADP(+). Replacing the hydrogenase with a ferredoxin-hydrogenase fusion switched the bias of electron transfer from FNR to hydrogenase and resulted in an increased rate of hydrogen photoproduction. These results suggest a new direction for improvement of biohydrogen production and a means to further resolve the mechanisms that control partitioning of photosynthetic electron transport.
光合作用水分解与氢化酶催化的氢气生产相耦合，被认为是一种很有前途的清洁、可再生能源。人们普遍认为，氢气生产的氧气敏感性，加上氢化酶与 NADPH 依赖性二氧化碳固定之间的竞争，是其商业化的主要限制因素。在这里，我们提供的证据表明，在支持氢气生产的厌氧条件下，体外 NADPH 生产过程中会有大量的光合电子损失。为了阐明竞争的基础，我们对铁氧还蛋白-氢化酶融合体进行了生物工程改造，并在存在 Fd、铁氧还蛋白：NADP(+)氧化还原酶 (FNR) 和 NADP(+)的情况下对氢气生产动力学进行了表征。用铁氧还蛋白-氢化酶融合体取代氢化酶将电子转移的偏向从 FNR 切换到氢化酶，从而导致氢气光生产速率增加。这些结果为生物氢气生产的改进提供了一个新的方向，并为进一步解决控制光合作用电子传递分配的机制提供了一种手段。
