SELECTIVE RELEASE OF ENZYMES FROM BACTERIA
SELECTIVE RELEASE OF ENZYMES FROM BACTERIA
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DOI：
10.1126/science.156.3781.1451
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发表时间：
1967-01-01
期刊：
影响因子：
56.9
通讯作者：
HEPPEL, LA
中科院分区：
文献类型：
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作者：
HEPPEL, LA
一组水解酶，包括磷酸酶和核酸酶，通过称为渗透压休克的过程从大肠杆菌和某些其它革兰氏阴性菌中选择性地释放出来。该程序涉及将细胞暴露于0. 5摩尔蔗糖，然后突然渗透转变为冷的稀MgCl2。渗透压休克还导致细菌细胞的渗透性屏障的改变和酸溶性核苷酸池的耗尽，但没有活力的丧失。在恢复到生长培养基中时，休克的细胞在滞后期后恢复。用EDTA和溶菌酶处理形成原生质球，导致选择性释放同一组酶。我们认为，选择性释放的酶被限制在细菌细胞壁和细胞质膜之间的区域。组织化学研究表明这样的定位。此外，即使当底物是核苷酸时，酶活性也可以用完整细胞测量，而整个细胞对核苷酸是不可渗透的。另一个证据是关于一种突变的E.具有缺陷细胞壁的大肠杆菌。与正常细菌不同，这种生物在生长过程中会将其中一种酶丢失到培养基中。在渗透压休克后，细菌显示硫酸盐、β-半乳糖苷、半乳糖和某些氨基酸的摄取减少。此外，休克处理导致释放能够结合硫酸盐、半乳糖和相同氨基酸的不可透析因子。这些观察结果的一个可能的解释是：结合蛋白占据的网站附近的细菌表面，它们可能是主动运输系统的组件负责这些营养物质的集中摄取。
A group of hydrolytic enzymes, including phosphatases and nucleases, is selectively released from Escherichia coli and certain other gram-negative bacteria by a process designated as osmotic shock. This procedure involves exposure of the cells to ethylenediaminetetraacetate (EDTA) in 0. 5 molar sucrose followed by a sudden osmotic transition to cold, dilute MgC12. Osmotic shock also results in an alteration of the permeability barrier of the bacterial cell and a depletion of the pool of acid-soluble nucleotides, but there is no loss of viability. On being restored to growth medium, the shocked cells recover after a lag period. Formation of spheroplasts by treatment with EDTA and lysozyme leads to selective release of the same group of enzymes. We believe that the selectively released enzymes are confined in a region between the bacterial cell wall and the cytoplasmic membrane. Histochemical studies indicate such a localization. Further, the enzyme activities are measurable with intact cells, even when the substrate is a nucleotide, to which whole cells are impermeable. Another piece of evidence concerns a mutant E. coli with a defective cell wall. In contrast to normal bacteria, this organism loses one of these enzymes into the medium in the course of growth. After osmotic shock, the bacteria show reduced uptake of sulfate, [beta]-galactosides, galactose, and certain amino acids. Furthermore, the shock treatment causes the release of nondialyzable factors able to bind sulfate, galactose, and the same amino acids. A possible interpretation of these observations is the following: the binding proteins occupy sites near the bacterial surface, and they may be components of active transport systems responsible for the concentrative uptake of these nutrients.