Homologous expression of aspartokinase (ask) gene in Streptomyces clavuligerus and its hom-deleted mutant: effects on cephamycin C production.
Homologous expression of aspartokinase (ask) gene in Streptomyces clavuligerus and its hom-deleted mutant: effects on cephamycin C production.
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DOI：
10.4161/bbug.1.3.11244
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发表时间：
2010-05-01
期刊：
影响因子：
--
通讯作者：
Piret, Jacqueline
中科院分区：
文献类型：
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作者：
Ozcengiz, Gulay;Okay, Sezer;Piret, Jacqueline
本研究研究了编码天冬氨酸激酶催化天冬氨酸途径第一步的ask基因的同源多拷贝对S. clavuligerus NRRL 3585及其homm突变体中头孢霉素C生物合成的影响。TB3585和AK39细胞内天冬氨酸途径氨基酸库水平与Ask活性水平一致。与未插入任何基因的对照菌株相比，在胰酶豆汤（TSB）和改良化学定义培养基（mCDM）中扩增ask基因的野生菌株，其特异性产量分别增加了3.1倍和3.3倍，体积产量分别增加了1.7倍和1.9倍。然而，当细胞在TSB或mCDM中生长时，多拷贝ask基因在同源缺失背景下的表达显著降低了头霉素C的产量，这很可能是由于在营养不良宿主中酶过表达和高拷贝数质粒负荷引起的生理干扰。
In this study, the effect of homologous multiple copies of the ask gene, which encodes aspartokinase catalyzing the first step of the aspartate pathway, on cephamycin C biosynthesis in S. clavuligerus NRRL 3585 and its hom mutant was investigated. The intracellular pool levels of aspartate pathway amino acids accorded well with the Ask activity levels in TB3585 and AK39. When compared with the control strain carrying vector alone without any gene insert, amplification of the ask gene in the wild strain resulted in a maximum of 3.1- and 3.3-fold increase in specific, 1.7- and 1.9-fold increase in volumetric cephamycin C production when grown in trypticase soy broth (TSB) and a modified chemically defined medium (mCDM), respectively. However, expression of multicopy ask gene in a hom-deleted background significantly decreased cephamycin C yields when the cells were grown in either TSB or mCDM, most probably due to physiological disturbance resulting from enzyme overexpression and high copy number plasmid burden in an auxotrophic host, respectively.