Over the last millennia, wetlands have been sequestering carbon from the atmosphere via photosynthesis at a higher rate than releasing it and, therefore, have globally accumulated 550 × 10¹⁵ g of carbon, which is equivalent to 73% of the atmospheric carbon pool. The accumulation of organic carbon in wetlands is effectuated by phenolic compounds, which suppress the degradation of soil organic matter by inhibiting the activity of organic-matter-degrading enzymes. The enzymatic removal of phenolic compounds by bacterial tyrosinases has historically been blocked by anoxic conditions in wetland soils, resulting from waterlogging. Bacterial tyrosinases are a subgroup of oxidoreductases that oxidatively remove phenolic compounds, coupled to the reduction of molecular oxygen to water. The biochemical properties of bacterial tyrosinases have been investigated thoroughly in vitro within recent decades, while investigations focused on carbon fluxes in wetlands on a macroscopic level have remained a thriving yet separated research area so far. In the wake of climate change, however, anoxic conditions in wetland soils are threatened by reduced rainfall and prolonged summer drought. This potentially allows tyrosinase enzymes to reduce the concentration of phenolic compounds, which in turn will increase the release of stored carbon back into the atmosphere. To offer compelling evidence for the novel concept that bacterial tyrosinases are among the key enzymes influencing carbon cycling in wetland ecosystems first, bacterial organisms indigenous to wetland ecosystems that harbor a TYR gene within their respective genome (tyr⁺) have been identified, which revealed a phylogenetically diverse community of tyr⁺ bacteria indigenous to wetlands based on genomic sequencing data. Bacterial TYR host organisms covering seven phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Planctomycetes, and Proteobacteria) have been identified within various wetland ecosystems (peatlands, marshes, mangrove forests, bogs, and alkaline soda lakes) which cover a climatic continuum ranging from high arctic to tropic ecosystems. Second, it is demonstrated that (in vitro) bacterial TYR activity is commonly observed at pH values characteristic for wetland ecosystems (ranging from pH 3.5 in peatlands and freshwater swamps to pH 9.0 in soda lakes and freshwater marshes) and toward phenolic compounds naturally present within wetland environments (p-coumaric acid, gallic acid, protocatechuic acid, p-hydroxybenzoic acid, caffeic acid, catechin, and epicatechin). Third, analyzing the available data confirmed that bacterial host organisms tend to exhibit in vitro growth optima at pH values similar to their respective wetland habitats. Based on these findings, it is concluded that, following increased aeration of previously anoxic wetland soils due to climate change, TYRs are among the enzymes capable of reducing the concentration of phenolic compounds present within wetland ecosystems, which will potentially destabilize vast amounts of carbon stored in these ecosystems. Finally, promising approaches to mitigate the detrimental effects of increased TYR activity in wetland ecosystems and the requirement of future investigations of the abundance and activity of TYRs in an environmental setting are presented.

中文翻译：

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酪氨酸酶在湿地生态系统中全球大量碳储存中的新作用

在过去的几千年里，湿地通过光合作用从大气中吸收碳的速度比释放它的速度要快，因此在全球范围内积累了 550 × 10 ¹⁵g 碳，相当于大气碳库的 73%。湿地有机碳的积累是通过酚类化合物来实现的，酚类化合物通过抑制有机质降解酶的活性来抑制土壤有机质的降解。历史上，细菌酪氨酸酶对酚类化合物的酶促去除一直被湿地土壤中的缺氧条件所阻碍，这是由涝渍引起的。细菌酪氨酸酶是氧化还原酶的一个亚组，可氧化去除酚类化合物，同时将分子氧还原为水。近几十年来，细菌酪氨酸酶的生化特性已在体外进行了彻底的研究，而在宏观水平上关注湿地碳通量的研究迄今为止仍然是一个蓬勃发展但又相互分离的研究领域。然而，随着气候变化，湿地土壤的缺氧条件受到降雨减少和夏季长期干旱的威胁。这可能使酪氨酸酶降低酚类化合物的浓度，从而增加储存的碳释放回大气中。为了为细菌酪氨酸酶是影响湿地生态系统碳循环的关键酶之一这一新概念提供令人信服的证据，首先，湿地生态系统中的细菌生物在其各自的基因组中含有 TYR 基因。这反过来又会增加储存的碳释放回大气中。为了为细菌酪氨酸酶是影响湿地生态系统碳循环的关键酶之一这一新概念提供令人信服的证据，首先，湿地生态系统中的细菌生物在其各自的基因组中含有 TYR 基因。这反过来又会增加储存的碳释放回大气中。为了为细菌酪氨酸酶是影响湿地生态系统碳循环的关键酶之一这一新概念提供令人信服的证据，首先，湿地生态系统中的细菌生物在其各自的基因组中含有 TYR 基因。tyr ⁺ ) 已被鉴定，这揭示了tyr ^{+的系统发育多样性群落}基于基因组测序数据的湿地原生细菌。在涵盖气候连续统一体的各种湿地生态系统（泥炭地、沼泽、红树林、沼泽和碱性苏打湖）中发现了细菌 TYR 宿主生物体，涵盖七个门（酸杆菌门、放线菌门、拟杆菌门、厚壁菌门、硝化螺菌门、Planctomycetes 和变形菌门）范围从北极高地到热带生态系统。其次，证明了（体外）细菌 TYR 活性通常在湿地生态系统特有的 pH 值（从泥炭地和淡水沼泽的 pH 值 3.5 到苏打湖和淡水沼泽的 pH 值 9.0）和天然存在的酚类化合物中观察到。湿地环境（对香豆酸、没食子酸、原儿茶酸、p-羟基苯甲酸、咖啡酸、儿茶素和表儿茶素）。第三，分析现有数据证实，细菌宿主生物倾向于在与其各自的湿地栖息地相似的 pH 值下表现出体外生长的最佳状态。基于这些发现，得出的结论是，由于气候变化导致以前缺氧的湿地土壤通气增加，TYRs 是能够降低湿地生态系统中酚类化合物浓度的酶之一，这可能会破坏大量储存的碳在这些生态系统中。最后，提出了减轻湿地生态系统中 TYR 活性增加的不利影响的有前景的方法，以及未来对环境环境中 TYR 的丰度和活性进行调查的要求。