Department of Environmental Biotechnology, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sadat City 32897, Egypt.
Biology Department, Science and Humanities College, Shaqra University, Al-Quwayiyah, 11726, Riyadh, Saudi Arabia.
Appl Microbiol Biotechnol. 2022 Sep;106(17):5539-5550. doi: 10.1007/s00253-022-12099-3. Epub 2022 Jul 30.
Rhizorhabdus (previously Sphingomonas) wittichii RW1 uses a diverse array of aromatic organic compounds as energy and carbon sources, including some extremely recalcitrant compounds such as dibenzo-p-dioxin and dibenzofuran. Extradiol dioxygenases play a key role in the metabolism of dibenzofuran (DBF), dibenzo-p-dioxin (DBD), PCBs, and various other aromatic compounds. In this study, a detailed kinetic analysis of four extradiol dioxygenases identified in R. wittichii RW1 (DbfB, Edo2, Edo3, and Edo4) showed all of them to be typical 2,3dihydroxybiphenyl (DHB) dioxygenases with DHB as preferred substrate (k/K values of 0.13-188 (µM s)) and only slightly lower activity against trihydroxybiphenyl (THB) whereas monocyclic substrates were, to different extents, poor substrates due to high k values. All extradiol dioxygenases analyzed were subject to mechanism-based inactivation by 2,2,3-trihydroxybiphenylether (THBE) the intermediate of DBD degradation. However, Edo4 was superior as reflected by the relatively high partition ratio and the comparably low efficiency of inactivation. Significant differences were observed with respect to their inactivation by 3-chlorocatechol. The absence of any significant mechanism-based inactivation makes Edo3 a perfect candidate for being recruited for chlorobiphenyl degradation where inactivation of extradiol dioxygenases by this intermediate creates significant metabolic problems. KEY POINTS: • Characterization of additional extradiol dioxygenases encoded by RW1 • Identification of differences in 2,2,3-trihydroxybiphenylether transformation • Identification of differences in inhibition by 3-chlorocatechol.
威氏硫杆菌（以前称为鞘氨醇单胞菌） RW1 可利用多种芳香族有机化合物作为能源和碳源，包括一些极其顽固的化合物，如二苯并对二恶英和二苯并呋喃。邻苯二酚 1,2-双加氧酶在二苯并呋喃（DBF）、二苯并对二恶英（DBD）、多氯联苯和其他各种芳香族化合物的代谢中起着关键作用。在这项研究中，对 RW1 中鉴定出的四种邻苯二酚 1,2-双加氧酶（DbfB、Edo2、Edo3 和 Edo4）进行了详细的动力学分析，结果表明它们都是典型的 2,3-二羟基联苯（DHB）双加氧酶，以 DHB 为首选底物（k/K 值为 0.13-188（µM s）），对三羟基联苯（THB）的活性略低，而单环底物由于 k 值较高，在不同程度上是较差的底物。所有分析的邻苯二酚 1,2-双加氧酶都受到 2,2,3-三羟基联苯醚（THBE）的机制失活，这是 DBD 降解的中间体。然而，Edo4 的相对较高的分配比和相对较低的失活效率表明其更为优越。在用 3-氯邻苯二酚进行失活时，观察到了显著的差异。Edo3 不存在任何明显的机制失活，使其成为招募用于氯联苯降解的理想候选物，其中该中间体对外源二酚 1,2-双加氧酶的失活会产生重大代谢问题。关键点： • 描述 RW1 编码的额外邻苯二酚 1,2-双加氧酶的特征 • 鉴定 2,2,3-三羟基联苯醚转化方面的差异 • 鉴定 3-氯邻苯二酚抑制方面的差异。
