During fermentation Escherichia coli transport succinate mainly via Dcu family carriers. Current paper describes the role of externally added succinate on N’N’-dicyclohexylcarbodiimide (DCCD) sensitive ATPase activity and H⁺ flux depending on potassium ions. At pH 7.5 in wild type membrane vesicles DCCD-sensitive ATPase activity was the same as in dcuACBD quadruple mutant. In dcuACB it was increased ~ 3.3 fold while in dcuD DCCD-sensitive ATPase activity was absent. The DCCD-sensitive H⁺ efflux was fully dependent on F_OF₁ only in dcuACB mutant. This activity depended on potassium ions and only in dcuACBD mutant DCCD-sensitive ATPase activity was stimulated ~ 3 fold. At pH 5.5 DCCD-sensitive ATPase activities were determined in dcuACB or dcuD mutants but not in wild type. Interestingly, addition of potassium ions enhanced DCCD-sensitive ATPase activity in dcuD mutant ~ 3-fold compared to wild type. In dcuD mutant ~ 3-fold higher H⁺ uptake was registered, compared to wild type. Taken together it can be concluded that at pH 7.5 the F_OF₁-activity depends on DcuACB. Moreover, DcuACB but not DcuD are working towards H⁺ uptake direction. DcuD contributes to H⁺ efflux at pH 7.5 while at pH 5.5 it affects H⁺ influx when external succinate is present.

在发酵过程中，大肠杆菌主要通过Dcu家族载体运输琥珀酸。当前的论文描述了外部添加的琥珀酸酯对N'N'-二环己基碳二亚胺（DCCD）敏感的ATPase活性和H ⁺取决于钾离子的通量的作用。在野生型膜囊泡的pH值为7.5时，DCCD敏感的ATPase活性与dcuACBD四重突变体中的相同。在dcuACB中，它增加了约3.3倍，而在dcuD中， DCCD敏感的ATPase活性却不存在。DCCD敏感的H ⁺流出仅在dcuACB中完全取决于F _O F ₁突变体。此活性取决于钾离子，仅在dcuACBD突变体中，DCCD敏感的ATPase活性被激发了约3倍。在pH 5.5下，在dcuACB或dcuD突变体中测定了DCCD敏感的ATPase活性，而在野生型中未测定。有趣的是，与野生型相比，在dcuD突变体中添加钾离子可提高DCCD敏感的ATPase活性约3倍。与野生型相比，在dcuD突变体中，H ⁺摄取量增加了约3倍。两者合计可以得出结论，在pH 7.5时，F _O F ₁活性取决于DcuACB。此外，DcuACB（而非DcuD）正在朝着H ⁺吸收方向。在pH 7.5时，DcuD有助于H ⁺流出，而在pH 5.5时，当存在外部琥珀酸酯时，DcuD会影响H ⁺流入。