Biochemical Characterization of 3-Methyl-4-nitrophenol Degradation in Burkholderia sp. Strain SJ98.
Biochemical Characterization of 3-Methyl-4-nitrophenol Degradation in Burkholderia sp. Strain SJ98.
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伯克霍尔德杆菌菌株 SJ98 降解 3-甲基-4-硝基苯酚的生化特性
DOI：
10.3389/fmicb.2016.00791
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发表时间：
2016
影响因子：
5.2
通讯作者：
Zhou NY
中科院分区：
文献类型：
--
作者：
Min J;Lu Y;Hu X;Zhou NY
据报道，有几种菌株在 3-甲基-4-硝基苯酚 (3M4NP) 上生长，3M4NP 是过量使用的杀虫剂杀螟松的主要分解产物。然而，3M4NP 在分子和生化水平上的微生物降解仍然未知。在这里，甲基-1,4-苯醌 (MBQ) 和甲基氢醌 (MHQ)，而不是之前提出的儿茶酚，被确定为伯克霍尔德杆菌降解 3M4NP 过程中环裂解前的中间体。菌株SJ98。实时定量 PCR 分析表明，参与对硝基苯酚 (PNP) 和 2-氯-4-硝基苯酚 (2C4NP) 分解代谢的 pnpABA1CDEF 簇也可能是该菌株中 3M4NP 降解的原因。纯化的 PNP 4-单加氧酶 (PnpA) 能够催化 3M4NP 单加氧生成 MBQ，并且对 3M4NP 的表观 Km 值为 20.3 ± 2.54 μM，并且 pnpA 对于通过基因敲除和互补进行的 3M4NP 分解代谢是绝对必要的。 PnpB 是一种 1,4-苯醌还原酶，可催化 MBQ 还原为 MHQ，并且还发现在体外将 3M4NP 转化为 MBQ 时可增强 PnpA 活性。通过连续催化测定，PnpCD、PnpE 和 PnpF 可能参与 3M4NP 分解代谢的下游途径。尽管 NpcCD、NpcE 和 NpcF 能够在体外催化 MHQ 的顺序转化，但这些酶不太可能参与 3M4NP 分解代谢，因为它们的编码基因不会因体内 3M4NP 诱导而上调。这些结果表明，参与 PNP 和 2C4NP 分解代谢的酶也负责菌株 SJ98 中 3M4NP 的降解。这填补了我们在分子和生化水平上理解 3M4NP 微生物降解的空白，并提供了另一个例子来说明结构相似化合物的微生物分解代谢的适应性灵活性。
Several strains have been reported to grow on 3-methyl-4-nitrophenol (3M4NP), the primary breakdown product of the excessively used insecticide fenitrothion. However, the microbial degradation of 3M4NP at molecular and biochemical levels remains unknown. Here, methyl-1,4-benzoquinone (MBQ) and methylhydroquinone (MHQ), rather than catechol proposed previously, were identified as the intermediates before ring cleavage during 3M4NP degradation by Burkholderia sp. strain SJ98. Real-time quantitative PCR analysis indicated that the pnpABA1CDEF cluster involved in para-nitrophenol (PNP) and 2-chloro-4-nitrophenol (2C4NP) catabolism was also likely responsible for 3M4NP degradation in this strain. Purified PNP 4-monooxygenase (PnpA) is able to catalyze the monooxygenation of 3M4NP to MBQ and exhibited an apparent Km value of 20.3 ± 2.54 μM for 3M4NP, and pnpA is absolutely necessary for the catabolism of 3M4NP by gene knock-out and complementation. PnpB, a 1,4-benzoquinone reductase catalyzes the reduction of MBQ to MHQ, and also found to enhance PnpA activity in vitro in the conversion of 3M4NP to MBQ. By sequential catalysis assays, PnpCD, PnpE, and PnpF were likely involved in the lower pathway of 3M4NP catabolism. Although NpcCD, NpcE, and NpcF are able to catalyze the sequential conversion of MHQ in vitro, these enzymes are unlikely involved in 3M4NP catabolism because their coding genes were not upregulated by 3M4NP induction in vivo. These results revealed that the enzymes involved in PNP and 2C4NP catabolism were also responsible for 3M4NP degradation in strain SJ98. This fills a gap in our understanding of the microbial degradation of 3M4NP at molecular and biochemical levels and also provides another example to illustrate the adaptive flexibility in microbial catabolism for structurally similar compounds.