Identification and characterization of a new three-component nicotinic acid hydroxylase NahAB(1)B(2) from Pusillimonas sp strain T2
Identification and characterization of a new three-component nicotinic acid hydroxylase NahAB(1)B(2) from Pusillimonas sp strain T2
复制标题
微单胞菌 T2 菌株中新型三组分烟酸羟化酶 NahAB(1)B(2) 的鉴定和表征
DOI：
10.1111/lam.12850
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发表时间：
2018
影响因子：
2.4
通讯作者：
Qiu J.
中科院分区：
文献类型：
--
作者：
Yuan M.;Zhang Y.;Zhao L.;Ma Y.;He Q.;He J.;Qiu J.
烟酸在自然界中普遍存在，其微生物降解机制多种多样。在这项研究中，Pusillimonassp。菌株T2能够利用NA作为唯一的碳氮源。该菌株在30℃、pH 7.0条件下可在3.5 h内完全降解300 mg l - 1NA， NA的降解中间体之一为6 -羟基烟酸（6HNA）。菌株T2的基因组草图序列全长为3.3 M bp，预计有3054个蛋白。鉴定了三组分NA羟化酶（NahAB1B2）基因的编码基因。hahab1b2基因在不降解NA的shinellasp中异源表达。应变HZN7。重组HZN7‐pBBR‐nahab1b2能将NA转化为等摩尔的6HNA，而重组HZN7‐pBBR‐nahAB1（缺乏组分B2）和HZN7‐pBBR‐nahAB2（缺乏组分B1）不能将NA转化为等摩尔的6HNA。HZN7 - pBBR - nahab1b2无细胞提取物显示NA羟化酶活性。添加人工电子受体（如phenazine methosulfate， PMS）后，NA羟化酶活性显著提高。以PMS为电子受体时，NA的kmandvmax值分别为65.94 μmol l−1和260·80±5.69 μ mg−1。本研究为细菌降解NA提供了新的视角。研究的意义和影响烟酸（NA）作为n -杂环芳香族化合物降解的模型系统，其微生物降解机制多种多样。这是首次鉴定出三组分羟化酶。本研究为细菌降解NA提供了新的视角。
Nicotinic acid (NA) is ubiquitous in nature and its microbial degradation mechanisms are diverse. In this study,Pusillimonassp. strain T2 was found to be capable of utilizing NA as sole carbon and nitrogen sources. This strain could completely degrade 300 mg l−1NA within 3·5 h at 30°C and pH 7·0 and one of the degradation intermediate of NA was identified as 6‐hydroxynicotinic acid (6HNA). The draft genome sequences of strain T2 were determined to have a total length of 3·3 M bp and 3054 proteins were predicted. The encoding genes of three‐component NA hydroxylase (NahAB1B2) genes were identified. ThenahAB1B2genes were heterologously expressed in the non‐NA‐degradingShinellasp. strain HZN7. The recombinant HZN7‐pBBR‐nahAB1B2converted NA into equimolar 6HNA, while the recombinants HZN7‐pBBR‐nahAB1(lacking component B2) and HZN7‐pBBR‐nahAB2(lacking component B1) could not convert NA. Cell‐free extracts of HZN7‐pBBR‐nahAB1B2exhibited NA hydroxylase activity. After addition of an artificial electron acceptor (such as phenazine methosulphate, PMS), the NA hydroxylase activity was significantly increased. TheKmandVmaxvalues for NA were 65·94μmol l−1and 260·80 ± 5·69 mU mg−1, respectively, using PMS as an electron acceptor. This study provides a novel insight into the NA degradation by bacteria.Significance and Impact of the StudyNicotinic acid (NA) serves as a model system for the degradation ofN‐heterocyclic aromatic compounds and the microbial degradation mechanisms are diverse. This is the first time that a three‐component hydroxylase has been identified. This study provides a novel insight into the NA degradation by bacteria.