A Novel Degradation Mechanism for Pyridine Derivatives in Alcaligenes faecalis JQ135
A Novel Degradation Mechanism for Pyridine Derivatives in Alcaligenes faecalis JQ135
复制标题
粪产碱菌 JQ135 中吡啶衍生物的新降解机制
DOI：
10.1128/aem.00910-18
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发表时间：
2018
影响因子：
4.4
通讯作者：
He Jian
中科院分区：
文献类型：
--
作者：
Qiu Jiguo;Liu Bin;Zhao Lingling;Zhang Yanting;Cheng Dan;Yan Xin;Jiang Ji;ong;Hong Qing;He Jian
与苯环不同，吡啶环的电子密度的不均匀分布影响位置反应性和与酶的相互作用;例如，邻位和帕拉氧化比Meta氧化更困难。羟基化是吡啶衍生物代谢的重要氧化过程。在以前的报道中，吡啶衍生物的邻位羟基化反应是由多组分的含氘单加氧酶催化的，而Meta羟基化反应是由单组分的依赖于FAD的单加氧酶催化的。本研究鉴定了新的单组分FAD依赖性单加氧酶HpaM，其催化5 HPA的邻位脱羧羟基化。此外，我们还发现，编码顺反异构酶的马亚基因在A. faecalis JQ 135.这项研究为吡啶衍生物的微生物代谢提供了新的见解。摘要5-羟基吡啶甲酸（5 HPA）是一种天然吡啶衍生物，在环境中会被微生物降解。然而，5 HPA代谢的生理、生化和遗传基础仍然未知。在这项研究中，操纵子（hpa），负责5 HPA降解，从粪产碱杆菌JQ 135克隆。HpaM是一种单组分的黄素腺嘌呤二核苷酸（FAD）依赖的单加氧酶，与已报道的单加氧酶的同源性较低（仅28 - 31%）。HpaM催化5 HPA邻位脱羧羟基化生成2，5-二羟基吡啶（2，5DHP）。HpaM的单加氧酶活性依赖于FAD和NADH。HpaM对5 HPA和NADH的表观Km值分别为45.4 μM和37.8 μM。发现hpaX、hpaD和hpaF基因分别编码2，5DHP双加氧酶、N-甲酰马来酰胺酸脱甲酰酶和马来酰胺酸酰胺水解酶，但这三个基因不是A. faecalis JQ 135.此外，马亚基因编码马来酸顺反异构酶，对A. faecalis JQ 135中，推测该基因可能是吡啶类化合物代谢的关键基因。本研究中鉴定的基因和蛋白质显示了一种新的吡啶衍生物降解机制。重要性与苯环不同，吡啶环的电子密度的不均匀分布影响位置反应性和与酶的相互作用;例如，邻位和帕拉氧化比Meta氧化更困难。羟基化是吡啶衍生物代谢的重要氧化过程。在以前的报道中，吡啶衍生物的邻位羟基化反应是由多组分的含氘单加氧酶催化的，而Meta羟基化反应是由单组分的依赖于FAD的单加氧酶催化的。本研究鉴定了新的单组分FAD依赖性单加氧酶HpaM，其催化5 HPA的邻位脱羧羟基化。此外，我们还发现，编码顺反异构酶的马亚基因在A. faecalis JQ 135.这项研究为吡啶衍生物的微生物代谢提供了新的见解。
Unlike the benzene ring, the uneven distribution of the electron density of the pyridine ring influences the positional reactivity and interaction with enzymes; e.g., the ortho and para oxidations are more difficult than the meta oxidations. Hydroxylation is an important oxidation process for the pyridine derivative metabolism. In previous reports, the ortho hydroxylations of pyridine derivatives were catalyzed by multicomponent molybdenum-containing monooxygenases, while the meta hydroxylations were catalyzed by monocomponent FAD-dependent monooxygenases. This study identified the new monocomponent FAD-dependent monooxygenase HpaM that catalyzed the ortho decarboxylative hydroxylation of 5HPA. In addition, we found that the maiA gene coding for maleic acid cis-trans isomerase was pivotal for the metabolism of 5HPA, nicotinic acid, and picolinic acid in A. faecalis JQ135. This study provides novel insights into the microbial metabolism of pyridine derivatives. ABSTRACT 5-Hydroxypicolinic acid (5HPA), a natural pyridine derivative, is microbially degraded in the environment. However, the physiological, biochemical, and genetic foundations of 5HPA metabolism remain unknown. In this study, an operon (hpa), responsible for 5HPA degradation, was cloned from Alcaligenes faecalis JQ135. HpaM was a monocomponent flavin adenine dinucleotide (FAD)-dependent monooxygenase and shared low identity (only 28 to 31%) with reported monooxygenases. HpaM catalyzed the ortho decarboxylative hydroxylation of 5HPA, generating 2,5-dihydroxypyridine (2,5DHP). The monooxygenase activity of HpaM was FAD and NADH dependent. The apparent Km values of HpaM for 5HPA and NADH were 45.4 μM and 37.8 μM, respectively. The genes hpaX, hpaD, and hpaF were found to encode 2,5DHP dioxygenase, N-formylmaleamic acid deformylase, and maleamate amidohydrolase, respectively; however, the three genes were not essential for 5HPA degradation in A. faecalis JQ135. Furthermore, the gene maiA, which encodes a maleic acid cis-trans isomerase, was essential for the metabolism of 5HPA, nicotinic acid, and picolinic acid in A. faecalis JQ135, indicating that it might be a key gene in the metabolism of pyridine derivatives. The genes and proteins identified in this study showed a novel degradation mechanism of pyridine derivatives. IMPORTANCE Unlike the benzene ring, the uneven distribution of the electron density of the pyridine ring influences the positional reactivity and interaction with enzymes; e.g., the ortho and para oxidations are more difficult than the meta oxidations. Hydroxylation is an important oxidation process for the pyridine derivative metabolism. In previous reports, the ortho hydroxylations of pyridine derivatives were catalyzed by multicomponent molybdenum-containing monooxygenases, while the meta hydroxylations were catalyzed by monocomponent FAD-dependent monooxygenases. This study identified the new monocomponent FAD-dependent monooxygenase HpaM that catalyzed the ortho decarboxylative hydroxylation of 5HPA. In addition, we found that the maiA gene coding for maleic acid cis-trans isomerase was pivotal for the metabolism of 5HPA, nicotinic acid, and picolinic acid in A. faecalis JQ135. This study provides novel insights into the microbial metabolism of pyridine derivatives.