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The membrane-bound sorbosone dehydrogenase of Gluconacetobacter liquefaciens is a pyrroloquinoline quinone-dependent enzyme
Enzyme and Microbial Technology ( IF 3.4 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.enzmictec.2020.109511
Toshiharu Yakushi 1 , Ryota Takahashi 2 , Minenosuke Matsutani 2 , Naoya Kataoka 1 , Roque A Hours 3 , Yoshitaka Ano 4 , Osao Adachi 5 , Kazunobu Matsushita 1
Affiliation  

Membrane-bound sorbosone dehydrogenase (SNDH) of Gluconacetobacter liquefaciens oxidizes l-sorbosone to 2-keto-l-gulonic acid (2KGLA), a key intermediate in vitamin C production. We constructed recombinant Escherichia coli and Gluconobacter strains harboring plasmids carrying the sndh gene from Ga. liquefaciens strain RCTMR10 to identify the prosthetic group of SNDH. The membranes of the recombinant E. coli showed l-sorbosone oxidation activity, only after the holo-enzyme formation with pyrroloquinoline quinone (PQQ), indicating that SNDH is a PQQ-dependent enzyme. The sorbosone-oxidizing respiratory chain was thus heterologously reconstituted in the E. coli membranes. The membranes that contained SNDH showed the activity of sorbosone:ubiquinone analogue oxidoreductase. These results suggest that the natural electron acceptor for SNDH is membranous ubiquinone, and it functions as the primary dehydrogenase in the sorbosone oxidation respiratory chain in Ga. liquefaciens. A biotransformation experiment showed l-sorbosone oxidation to 2KGLA in a nearly quantitative manner. Phylogenetic analysis for prokaryotic SNDH homologues revealed that they are found only in the Proteobacteria phylum and those of the Acetobacteraceae family are clustered in a group where all members possess a transmembrane segment. A three-dimensional structure model of the SNDH constructed with an in silico fold recognition method was similar to the crystal structure of the PQQ-dependent pyranose dehydrogenase from Coprinopsis cinerea. The structural similarity suggests a reaction mechanism under which PQQ participates in l-sorbosone oxidation.

中文翻译:

液化葡萄糖乙酸杆菌的膜结合山梨糖酮脱氢酶是一种吡咯并喹啉醌依赖性酶

液化葡萄糖乙酸杆菌的膜结合山梨糖酮脱氢酶 (SNDH) 将 l-山梨糖酮氧化为 2-酮-l-古洛糖酸 (2KGLA),这是维生素 C 生产的关键中间体。我们构建了含有携带来自 Ga. liquefaciens 菌株 RCTMR10 的 sndh 基因的质粒的重组大肠杆菌和葡糖杆菌菌株,以鉴定 SNDH 的假体组。只有在与吡咯并喹啉醌 (PQQ) 形成全酶后,重组大肠杆菌的膜才显示出 l-山梨糖酮氧化活性,表明 SNDH 是 PQQ 依赖性酶。因此,山梨糖酮氧化呼吸链在大肠杆菌膜中异源重组。含有 SNDH 的膜显示了山梨糖酮:泛醌类似物氧化还原酶的活性。这些结果表明 SNDH 的天然电子受体是膜质泛醌,它是 Ga. liquefaciens 山梨糖酮氧化呼吸链中的主要脱氢酶。生物转化实验表明,L-山梨糖酮以近乎定量的方式氧化为 2KGLA。原核 SNDH 同源物的系统发育分析表明,它们仅存在于变形杆菌门中,而醋杆菌科的同源物聚集在一个所有成员都具有跨膜片段的组中。用计算机折叠识别方法构建的 SNDH 三维结构模型与来自鬼伞的 PQQ 依赖性吡喃糖脱氢酶的晶体结构相似。结构相似性表明 PQQ 参与 l-山梨糖酮氧化的反应机制。
更新日期:2020-06-01
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