PDF(Pubmed)
Abstract：
Methanethiol (MT) is a sulfur-containing compound produced during dimethylsulfoniopropionate (DMSP) degradation by marine bacteria. The C-S bond of MT can be cleaved by methanethiol oxidases (MTOs) to release a sulfur atom. However, the cleaving process remains unclear, and the species of sulfur product is uncertain. It has long been assumed that MTOs produce hydrogen sulfide (H2S) from MT. Herein, we studied the MTOs in the Rhodobacteraceae family-whose members are important DMSP degraders ubiquitous in marine environments. We identified 57 MTOs from 1,904 Rhodobacteraceae genomes. These MTOs were grouped into two major clusters. Cluster 1 members share three conserved cysteine residues, while cluster 2 members contain one conserved cysteine residue. We examined the products of three representative MTOs both in vitro and in vivo. All of them produced sulfane sulfur other than H2S from MT. Their conserved cysteines are substrate-binding sites in which the MTO-S-S-CH3 complex is formed. This finding clarified the sulfur product of MTOs and enlightened the MTO-catalyzing process. Moreover, this study connected DMSP degradation with sulfane sulfur metabolism, filling a critical gap in the DMSP degradation pathway and representing new knowledge in the marine sulfur cycle field.
OBJECTIVE: This study overthrows a long-time assumption that methanethiol oxidases (MTOs) cleave the C-S bond of methanethiol to produce both H2S and H2O2-the former is a strong reductant and the latter is a strong oxidant. From a chemistry viewpoint, this reaction is difficult to happen. Investigations on three representative MTOs indicated that sulfane sulfur (S0) was the direct product, and no H2O2 was produced. Finally, the products of MTOs were corrected to be S0 and H2O. This finding connected dimethylsulfoniopropionate (DMSP) degradation with sulfane sulfur metabolism, filling a critical gap in the DMSP degradation pathway and representing new knowledge in the marine sulfur cycle field.
OBJECTIVE: This study overthrows a long-time assumption that methanethiol oxidases (MTOs) cleave the C-S bond of methanethiol to produce both H2S and H2O2-the former is a strong reductant and the latter is a strong oxidant. From a chemistry viewpoint, this reaction is difficult to happen. Investigations on three representative MTOs indicated that sulfane sulfur (S0) was the direct product, and no H2O2 was produced. Finally, the products of MTOs were corrected to be S0 and H2O. This finding connected dimethylsulfoniopropionate (DMSP) degradation with sulfane sulfur metabolism, filling a critical gap in the DMSP degradation pathway and representing new knowledge in the marine sulfur cycle field.
摘要：
甲硫醇（MT）是海洋细菌在二甲基磺丙酸酯（DMSP）降解过程中产生的含硫化合物。MT的C-S键可以被甲硫醇氧化酶(MTO)裂解以释放硫原子。然而,裂开过程尚不清楚,硫产品的种类不确定。长期以来，人们一直认为MTO从MT产生硫化氢（H2S）。在这里，我们研究了红杆菌科的MTO，其成员是海洋环境中普遍存在的重要DMSP降解剂。我们从1,904个红杆菌科基因组中鉴定出57个MTO。这些MTO被分为两个主要的集群。簇1成员共享三个保守的半胱氨酸残基，而簇2成员含有一个保守的半胱氨酸残基。我们在体外和体内检查了三种代表性MTO的产物。它们都从MT中产生除H2S以外的硫烷硫。它们保守的半胱氨酸是形成MTO-S-S-CH3复合物的底物结合位点。这一发现澄清了MTO的硫产物，并启发了MTO催化过程。此外，这项研究将DMSP降解与硫烷硫代谢联系起来，填补了DMSP降解途径中的关键空白，并代表了海洋硫循环领域的新知识。重要意义这项研究推翻了长期以来的假设，即甲硫醇氧化酶（MTOs）裂解甲硫醇的C-S键，产生H2S和H2O2-前者是强还原剂，后者是强氧化剂。从化学的角度来看，这种反应很难发生。对三个有代表性的MTO的调查表明，硫烷硫(S0)是直接产物，并且没有产生H2O2。最后,MTOs的产物校正为S0和H2O。这一发现将二甲基磺丙酸酯（DMSP）降解与硫烷硫代谢联系起来，填补了DMSP降解途径中的关键空白，并代表了海洋硫循环领域的新知识。
