Ducluzeau Anne-Lise, Schoepp-Cothenet Barbara, van Lis Robert, Baymann Frauke, Russell Michael J, Nitschke Wolfgang
Beadle Center, University of Nebraska-Lincoln, 1901 Vine Street, Lincoln, NE 68588-0660, USA.
Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/AMU, FR3479, Marseille Cedex 20 13402, France.
J R Soc Interface. 2014 Sep 6;11(98):20140196. doi: 10.1098/rsif.2014.0196.
Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes.
地球上复杂的生命形式至关重要地依赖于高度氧化的分子氧几乎无处不在所提供的强大氧化还原不平衡。然而，大气中氧气水平的历史是复杂的，在约23亿年前的大氧化事件之前，与当今的值相比，生物圈中的氧气量被认为极低。因此，生命和氧气水平的进化历史可能错综复杂地交织在一起。推断氧气水平变化对生命影响的明显生物学指标是酶的进化历史，这种酶使生物体能够利用分子氧的氧化还原能力，即生物能量氧气还原酶，别名细胞色素和喹啉氧化酶。因此，在过去二十年中，为这个酶超家族重建的分子系统发育已被用于试图阐明环境中的氧气水平与呼吸生物能量过程进化之间的相互联系。尽管基于完全相同的数据集，但这些系统发育方法在地球酶超家族和分子氧的历史方面导致了截然相反的情况。为了克服分子系统发育的僵局，我们在这里回顾目前与该超家族进化相关的可用结构、功能、古地球化学和热力学信息（该超家族尤其还包括一氧化氮还原酶亚家族）。在我们看来，最符合这些非系统发育数据总体情况的设想是，低氧亲和力的SoxM-（或A-）型酶是最新的进化创新，而高亲和力的氧气还原酶（SoxB或B和cbb3或C）独立于还原一氧化氮的前体酶产生。
