Exogenous 5,6-dimethylbenzimidazole caused production of a non-functional tetrachloroethene reductive dehalogenase in Sulfurospirillum multivorans
Exogenous 5,6-dimethylbenzimidazole caused production of a non-functional tetrachloroethene reductive dehalogenase in Sulfurospirillum multivorans
复制标题
DOI：
10.1111/1462-2920.12268
复制
发表时间：
2014-11-01
影响因子：
5.1
通讯作者：
Schubert, Torsten
中科院分区：
文献类型：
--
作者：
Keller, Sebastian;Ruetz, Markus;Schubert, Torsten
类咕啉依赖性还原脱卤是由遗传多样性厌氧菌介导的，这些厌氧菌要么重新合成类咕啉，要么依赖于从环境中回收的类咕啉。革兰氏阴性ε-变形杆菌多噬硫杆菌的四氯乙烯还原性脱卤酶（PceA）含有一个去甲假B-12作为类咕啉辅因子。去甲假-B-12在核苷酸环结构上不同于辅酶B-12。腺嘌呤代替5，6-二甲基苯并咪唑（DMB）作为中心钴离子的较低配体碱基，并且norpseudo-B-12的核苷酸环在位置176处缺少甲基。在本研究中，在DMB存在下，使多噬链球菌与PCE厌氧生长。在25 M的DMB浓度下，去甲假-B-12的核苷酸环中的腺嘌呤部分被DMB定量取代。含DMB的nor-B-12的形成严重影响PCE依赖的生长和PceA活性。在DMB处理的细胞中，细胞质PceA前体的加工受到阻碍，这一结果指向延迟的辅因子掺入。从用DMB培养的细胞富集的PceA含有nor-B-12。从在DMB存在下生长的细胞中纯化的Nor-B-12介导三氯乙酸到二氯乙酸的非生物还原脱卤，与norpseudo-B-12相比，其速率低25倍，这一事实支持norpseudo-B-12作为一般还原脱卤的有效催化剂的相关性。
Corrinoid-dependent reductive dehalogenation is mediated by phylogenetically diverse anaerobic bacteria that either synthesize corrinoids de novo or are dependent on corrinoid salvaging from the environment. The tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-negative Epsilonproteobacterium Sulfurospirillum multivorans harbours a norpseudo-B-12 as corrinoid cofactor. Norpseudo-B-12 differs from coenzyme B-12 in the nucleotide loop structure. Adenine instead of 5,6-dimethylbenzimidazole (DMB) serves as lower ligand base of the central cobalt ion, and the nucleotide loop of norpseudo-B-12 lacks a methyl group at position 176. In this study, S.multivorans was grown anaerobically with PCE in the presence of DMB. At a DMB concentration of 25M, the adenine moiety in the nucleotide loop of norpseudo-B-12 was quantitatively replaced by DMB. The formation of the DMB-containing nor-B-12 severely affected PCE-dependent growth and the PceA activity. In DMB-treated cells processing of the cytoplasmic PceA precursor was impeded, a result pointing to retarded cofactor incorporation. PceA enriched from cells cultivated with DMB contained nor-B-12. Nor-B-12 purified from cells grown in the presence of DMB mediated the abiotic reductive dehalogenation of trichloroacetate to dichloroacetate at a 25-fold lower rate in comparison with norpseudo-B-12, a fact underpinning the relevance of norpseudo-B-12 as efficient catalyst for reductive dehalogenation in general.