Transport of p-nitrophenyl-alpha-maltoside by the maltose transport system of Escherichia coli and its subsequent hydrolysis by a cytoplasmic alpha-maltosidase.
Transport of p-nitrophenyl-alpha-maltoside by the maltose transport system of Escherichia coli and its subsequent hydrolysis by a cytoplasmic alpha-maltosidase.
复制标题
通过大肠杆菌的麦芽糖转运系统转运对硝基苯基-α-麦芽糖苷，并随后通过细胞质α-麦芽糖苷酶进行水解。
DOI：
10.1128/jb.165.3.918-922.1986
复制
发表时间：
1986
影响因子：
3.2
通讯作者：
Shuman,HA
中科院分区：
文献类型：
--
作者：
Reyes,M;Treptow,NA;Shuman,HA
在野生型大肠杆菌中，麦芽糖转运系统的活性依赖于周质麦芽糖结合蛋白。然而，已经有可能分离出其中转运活性由系统的膜组分介导并且不再依赖于周质结合蛋白的突变体。在这份手稿中，我们表明，在这些结合蛋白的独立菌株，对硝基苯基-α-麦芽糖苷是一种有效的麦芽糖转运抑制剂。相比之下，对硝基苯基-α-麦芽糖苷仅是野生型细菌中麦芽糖转运的弱抑制剂。此外，我们表明，对硝基苯基-α-麦芽糖苷是由结合蛋白的独立菌株，但不是由野生型细菌运输。我们能够检测到这种化合物的运输，因为有一种细胞质酶可以切割对硝基苯基-α-麦芽糖苷。这种酶以前没有被描述过。我们表明，虽然这种酶的合成受到相同的调节作为麦芽糖调节子的组成部分，是麦芽糖依赖，它不是由一个已知的mal基因编码。我们将这种酶称为α-麦芽糖苷酶。这些结果加强了我们的建议，麦芽糖转运系统的膜组件包括麦芽糖和相关底物的识别位点。
In wild-type Escherichia coli the activity of the maltose transport system is dependent on a periplasmic maltose-binding protein. It has been possible, however, to isolate mutants in which transport activity is mediated by the membrane components of the system and is no longer dependent on the periplasmic binding protein. In this manuscript we show that in these binding protein-independent strains, p-nitrophenyl-alpha-maltoside is a potent inhibitor of maltose transport. In contrast, p-nitrophenyl-alpha-maltoside is only a weak inhibitor of maltose transport in wild-type bacteria. In addition, we show that p-nitrophenyl-alpha-maltoside is transported by the binding protein-independent strains but not by wild-type bacteria. We were able to detect transport of this compound because there is a cytoplasmic enzyme that cleaves p-nitrophenyl-alpha-maltoside. This enzyme has not previously been described. We show that although the synthesis of this enzyme is subject to the same regulation as the components of the maltose regulon, and is MalT dependent, it is not coded for by a known mal gene. We refer to this enzyme as alpha-maltosidase. These results strengthen our proposal that the membrane components of the maltose transport system comprise a recognition site for maltose and related substrates.