Nonspecific inhibition of proline dehydrogenase synthesis in Escherichia coli during osmotic stress.
Nonspecific inhibition of proline dehydrogenase synthesis in Escherichia coli during osmotic stress.
复制标题
渗透胁迫期间大肠杆菌脯氨酸脱氢酶合成的非特异性抑制。
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
V. J. Stone
中科院分区：
文献类型：
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作者：
C. Deutch;J. M. Hasler;R. M. Houston;M. Sharma;V. J. Stone
大肠杆菌在高渗透压培养基中生长时积累的L-脯氨酸也诱导将其降解为谷氨酸的酶的合成。为了确定在渗透胁迫期间脯氨酸催化酶是否被抑制，在不同浓度的NaCl和蔗糖中检查脯氨酸利用和脯氨酸脱氢酶的形成。虽然E.大肠杆菌与脯氨酸作为唯一的氮源减少的溶质渗透压的增加，在生长速率发生了类似的减少与铵作为主要的氮源。通过[14 C]脯氨酸转化为[14 C]谷氨酸盐在全细胞中测量的脯氨酸催化剂仅受到高达1.0 μ l/kg的溶质渗透压的轻微抑制;在2.0 μ l/kg时仍发现超过50%的初始活性。相比之下，在添加溶质的存在下生长的细菌中的脯氨酸脱氢酶的比活性下降到低于对照水平的20%。这种减少与较低的合成速率有关，但与目前已知参与脯氨酸调节或脯氨酸代谢的基因无关。在相似的生长条件下，异硫氰酸酯酶、β-半乳糖苷酶和组氨醇脱氢酶的比活性也降低。这些结果表明，虽然脯氨酸catalysts不直接抑制高溶质浓度，长期暴露于渗透胁迫导致其减少作为一个更一般的代谢反应的一部分。
L-Proline, which is accumulated by Escherichia coli during growth in media of high osmolality, also induces the synthesis of the enzyme degrading it to glutamate. To determine if proline catabolism is inhibited during osmotic stress, proline utilization and the formation of proline dehydrogenase were examined in varying concentrations of NaCl and sucrose. Although the specific growth rate of E. coli with proline as the sole nitrogen source diminished as the solute osmolality increased, a comparable reduction in growth rate occurred with ammonium as the primary nitrogen source. Proline catabolism, as measured in whole cells by the conversion of [14C]proline to [14C]glutamate, was only slightly inhibited by solute osmolalities up to 1.0 osmol/kg; more than 50% of the initial activity was still found at 2.0 osmol/kg. By contrast, the specific activity of proline dehydrogenase in bacteria grown in the presence of added solutes decreased to less than 20% of the control level. This reduction was related to a lower rate of synthesis, but was independent of genes currently known to be involved in osmoregulation or proline metabolism. The specific activities of tryptophanase, beta-galactosidase, and histidinol dehydrogenase were also reduced under similar growth conditions. These results indicate that while proline catabolism is not directly inhibited by high solute concentrations, prolonged exposure to osmotic stress leads to its reduction as part of a more general metabolic response.
DOI：
10.1073/pnas.78.1.464
发表时间：
1981-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
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作者：
LAIMINS, LA;RHOADS, DB;EPSTEIN, W
通讯作者：
EPSTEIN, W