Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
J Appl Microbiol. 2009 Apr;106(4):1140-6. doi: 10.1111/j.1365-2672.2008.04079.x. Epub 2009 Jan 15.
Ebosin, a novel exopolysaccharide (EPS) produced by Streptomyces sp. 139 has antagonistic activity for interleukin-1 receptor (IL-1R) in vitro and remarkable anti-rheumatic arthritis activity in vivo. Ebosin biosynthesis gene (ste) cluster has been identified in our laboratory. This paper reports our effort to characterize the function of ste11 gene.
After the ste11 gene was cloned and expressed in Escherichia coli BL21, the recombinant Ste11 was purified and found capable of catalyzing NAD(+) and l-threonine to NADH and 2-amino-3-ketobutyrate, hence identified as a threonine dehydrogenase (TDH). To investigate its function in the biosynthesis of Ebosin, the ste11 gene was knocked out with a double crossover via homologous recombination. The monosaccharide composition of EPS produced by the mutant strain (EPS-m) was altered from that of Ebosin. The analysis of IL-1R antagonist activity for EPSs showed that the bioactivity of EPS-m was lower than Ebosin.
ste11 gene encoding a TDH may function as a modifier gene of Ebosin during its biosynthesis.
TDH encoded by ste11 is functional in Ebosin biosynthesis. It is the first characterized TDH in Streptomyces.
由链霉菌 sp.139 产生的新型胞外多糖（EPS）埃博霉素在体外具有白细胞介素-1 受体（IL-1R）拮抗活性，在体内具有显著的抗风湿性关节炎活性。我们实验室已经鉴定出埃博霉素生物合成基因（ste）簇。本文报告了我们对 ste11 基因功能进行表征的努力。
在将 ste11 基因克隆并在大肠杆菌 BL21 中表达后，纯化了重组 Ste11，发现其能够催化 NAD(+)和 l-苏氨酸生成 NADH 和 2-氨基-3-酮丁酸，因此被鉴定为苏氨酸脱氢酶（TDH）。为了研究其在埃博霉素生物合成中的功能，通过同源重组进行了 ste11 基因的双交换敲除。突变株（EPS-m）产生的 EPS 的单糖组成与埃博霉素不同。对 EPSs 的 IL-1R 拮抗剂活性分析表明，EPS-m 的生物活性低于埃博霉素。
编码 TDH 的 ste11 基因可能在埃博霉素生物合成中作为修饰基因发挥作用。
由 ste11 编码的 TDH 在埃博霉素生物合成中具有功能。它是链霉菌中第一个被表征的 TDH。
