Melis A, Zhang L, Forestier M, Ghirardi M L, Seibert M
Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, California 94720-3102, USA.
Plant Physiol. 2000 Jan;122(1):127-36. doi: 10.1104/pp.122.1.127.
The work describes a novel approach for sustained photobiological production of H(2) gas via the reversible hydrogenase pathway in the green alga Chlamydomonas reinhardtii. This single-organism, two-stage H(2) production method circumvents the severe O(2) sensitivity of the reversible hydrogenase by temporally separating photosynthetic O(2) evolution and carbon accumulation (stage 1) from the consumption of cellular metabolites and concomitant H(2) production (stage 2). A transition from stage 1 to stage 2 was effected upon S deprivation of the culture, which reversibly inactivated photosystem II (PSII) and O(2) evolution. Under these conditions, oxidative respiration by the cells in the light depleted O(2) and caused anaerobiosis in the culture, which was necessary and sufficient for the induction of the reversible hydrogenase. Subsequently, sustained cellular H(2) gas production was observed in the light but not in the dark. The mechanism of H(2) production entailed protein consumption and electron transport from endogenous substrate to the cytochrome b(6)-f and PSI complexes in the chloroplast thylakoids. Light absorption by PSI was required for H(2) evolution, suggesting that photoreduction of ferredoxin is followed by electron donation to the reversible hydrogenase. The latter catalyzes the reduction of protons to molecular H(2) in the chloroplast stroma.
这项工作描述了一种通过莱茵衣藻中可逆氢化酶途径持续光生物制氢的新方法。这种单细胞两阶段制氢方法通过暂时分离光合放氧和碳积累（阶段1）与细胞代谢物消耗及伴随的产氢过程（阶段2），规避了可逆氢化酶对氧气的高度敏感性。当培养物缺硫时，实现了从阶段1到阶段2的转变，这会使光系统II（PSII）和放氧过程可逆失活。在这些条件下，细胞在光照下进行氧化呼吸消耗氧气，导致培养物中出现厌氧状态，这对于诱导可逆氢化酶是必要且充分的。随后，在光照下观察到细胞持续产氢，而在黑暗中则没有。产氢机制涉及蛋白质消耗以及电子从内源性底物传递到叶绿体类囊体中的细胞色素b(6)-f和PSI复合物。产氢需要PSI吸收光，这表明铁氧还蛋白的光还原之后是向可逆氢化酶的电子供体过程。后者在叶绿体基质中催化质子还原为分子氢。
