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首页> 美国卫生研究院文献>Biochemical Journal >Utilization of gluconate by Escherichia coli. Uptake of d-gluconate by a mutant impaired in gluconate kinase activity and by membrane vesicles derived therefrom
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Utilization of gluconate by Escherichia coli. Uptake of d-gluconate by a mutant impaired in gluconate kinase activity and by membrane vesicles derived therefrom

机译：大肠杆菌对葡萄糖酸盐的利用。葡萄糖酸激酶活性受损的突变体和由其衍生的膜囊泡对d-葡萄糖酸酯的摄取

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1. From Escherichia coli strain K2.1.5c.8.9, which is devoid of 6-phosphogluconate dehydrogenase (gnd) and 6-phosphogluconate dehydratase (edd) activities, a mutant R6 was isolated that was tolerant to gluconate though still edd−, gnd−. 2. Measurements of the fate of labelled gluconate, of the conversion of gluconate into 6-phosphogluconate, and of the induction of gluconate kinase by the two organisms show that, although both inducibly form a gluconate-transport system, strain R6 is impaired in its ability to convert the gluconate thus taken up into 6-phosphogluconate; it was therefore used for study of the kinetics and energetics of gluconate uptake. 3. Suspensions of strain R6 induced for gluconate uptake took up this substrate via a `high affinity' transport process, with Km about 10μm and Vmax. about 25nmol/min per mg dry mass; a `low affinity' system demonstrated to occur in certain E. coli mutants was not induced under the conditions used in this work. 4. The uptake of gluconate was inhibited by lack of oxygen and by inhibitors of electron transport; such inhibitors also promoted the efflux of gluconate taken up. 5. Membrane vesicles prepared from strain R6 also manifested these properties when incubated with suitable electron donors, at rates similar to those observed with whole cells. 6. The results indicate that the active transport of gluconate into the cells is the rate-limiting step in gluconate utilization by E. coli, and that the mechanism of this process can be validly studied with membrane vesicles.
机译：1.从大肠杆菌菌株K2.1.5 c .8.9，该菌株没有6-磷酸葡萄糖酸脱氢酶（gnd）和6-磷酸葡萄糖酸脱水酶（edd）活性，分离出了耐受R6的突变体R6。葡萄糖酸盐虽然仍然是edd -，gnd -。 2.两种生物对标记的葡萄糖酸盐的命运，葡萄糖酸盐转化为6-磷酸葡萄糖酸盐的诱导以及葡萄糖酸盐激酶的诱导的测量结果表明，尽管两者都可诱导形成葡萄糖酸盐转运系统，但菌株R6的受损将摄取的葡萄糖酸酯转化为6-磷酸葡萄糖酸酯的能力；因此，它被用于研究葡萄糖酸盐吸收的动力学和能量学。 3.诱导葡萄糖酸盐吸收的菌株R6的悬浮液通过“高亲和力”转运过程吸收了该底物，Km约为10μm，Vmax。每毫克干物质约25nmol / min;在这项工作中使用的条件下，没有诱导出在某些大肠杆菌突变体中出现的“低亲和力”系统。 4.缺氧和电子传输抑制剂抑制了葡萄糖酸盐的摄取。这类抑制剂还促进了葡萄糖酸盐的外排。 5.当与合适的电子供体一起孵育时，由菌株R6制备的膜囊泡也表现出这些特性，其速率类似于在全细胞中观察到的速率。 6.结果表明，葡萄糖酸盐向细胞内的主动转运是大肠杆菌利用葡萄糖酸盐的限速步骤，并且该过程的机制可以通过膜囊泡进行有效研究。

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