Biochemical Barriers on the Path to Ocean Anoxia?
Biochemical Barriers on the Path to Ocean Anoxia?
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DOI：
10.1128/mbio.01332-21
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发表时间：
2021-08-31
期刊：
影响因子：
6.4
通讯作者：
Wolf S
中科院分区：
文献类型：
--
作者：
Giovannoni S;Chan F;Davis E 2nd;Deutsch C;Wolf S
微生物呼吸的动力学表明，如果存在过量的有机物，则氧气应在Michaelis-Menten常数（Km）的范围内下降到纳摩尔水平。然而，即使在许多具有生物生产力的沿海地区，观测到的最低O2浓度往往仍然比呼吸Km值高几个数量级。我们提出缺氧屏障假说（HBH）来解释这种明显的差异。HBH假设参与有机物分解的氧化酶在动力学上受到浓度远高于呼吸阈值的O2的限制。我们在文献中报告的1，137个O2 Km值的荟萃分析中发现了HBH的支持：末端呼吸氧化酶的中位数为350 nM，但其他氧化酶类型的中位数为67 μM。HBH将我们的注意力引向一类重要的氧依赖反应的动力学特性，这可能有助于解释海洋生态系统经历O2压力的轨迹。
The kinetics of microbial respiration suggests that, if excess organic matter is present, oxygen should fall to nanomolar levels in the range of the Michaelis-Menten constants (Km). Yet even in many biologically productive coastal regions, lowest observed O2 concentrations often remain several orders of magnitude higher than respiratory Km values. We propose the hypoxic barrier hypothesis (HBH) to explain this apparent discrepancy. The HBH postulates that oxidative enzymes involved in organic matter catabolism are kinetically limited by O2 at concentrations far higher than the thresholds for respiration. We found support for the HBH in a meta-analysis of 1,137 O2 Km values reported in the literature: the median value for terminal respiratory oxidases was 350 nM, but for other oxidase types, the median value was 67 μM. The HBH directs our attention to the kinetic properties of an important class of oxygen-dependent reactions that could help explain the trajectories of ocean ecosystems experiencing O2 stress.