Na^+调节天蓝淡红链霉菌突变株SIPI1482-NS-4合成柔红霉素的机制研究

Studies on the of regulatory mechanism of Na^+ on daunorubicin biosynthesis

SIPI 1482 - NS- 4是柔红霉素的产生菌天蓝淡红链霉菌 SIPI 1482的阻断突变株 ,不能合成柔红霉素。研究发现 Na+对 SIPI1482 - NS- 4恢复合成柔红霉素具有调节作用。在 GM培养基中添加 2 % Na Cl后 ,虽然突变株的菌体生长量降低 ,细胞脂肪含量下降 ,电镜还观察到细胞中脂肪颗粒显著减少 ,但不产抗生素的负突变株 SIPI 1482 - NS- 4却恢复合成柔红霉素 ,推测 Na+的这种调节作用可能同初级代谢与次级代谢之间的代谢流向有关。检测突变株 SIPI 1482 - NS- 4在 GM培养基和 GM+2 % Na Cl培养基中 ,催化柔红霉素前体丙酰 Co A合成的甲基丙二酰 Co A羧基转移酶 (MCT)和甲基丙二酰 Co A脱羧酶 (MDC)的活力变化 ,结果发现在 GM培养基中 MCT酶和 MDC酶的活力很低 ,但添加了 2 % Na Cl后 ,伴随着柔红霉素的恢复合成 ,MDC酶活力迅速提高。说明 SIPI 1482 - NS- 4的阻断突变与前体丙酰 Co A有关 ,Na+诱导了 MDC酶 ,从而前体丙酰 Co A重新合成 ,突变株恢复合成柔红霉素。亲株 SIPI 1482在 GM培养基中 ,MDC酶的活力很低 ,但 MCT酶的活力和柔红霉素的生物合成有一定的相关性 ;培养基添加 2 % Na Cl后 ,MDC酶的活力上升 ,柔红霉素产量提高。说明在 SIPI1482中 ,柔红霉素前体丙酰 Co A主要是通过 MCT酶途径催化而生成的 。

The blocked mutant SIPI 1482 NS 4 which was derived from Streptomyces coeruleorubidus SIPI 1482, an organism that produced daunorubicin,was lack to produce daunorubicin. It was found that the mutant restored the daunorubicin productivity when 2% NaCl was added to GM medium, though it reduced mycelial biomass and diminished lipid synthesis, and there were less fatty granules in the ultra structure cell observed with electron microscope. It was elucidated that the regulatory of Na + had relation to the primary metabolism changing to the secondary metabolism according to the similar pathway between fatty biosynthesis and daunorubicin biosynthesis. The enzyme activities of methylmalonyl CoA pyruvate transcarboxylase (MCT) and methylmalonyl CoA decarboxylase (MDC) of SIPI 1482 NS 4 in GM medium with or without 2% NaCl, which catalyzed the formation of propionyl CoA, were tested. Results showed that the enzyme activities of MCT and MDC were lowered in GM medium, while the enzyme activity of MDC increased and daunorubicin reproduced in GM+2% NaCl medium. It was suggested that the blocked mutant of SIPI 1482 NS 4 had relation to the precursor propionyl CoA . MDC was induced by NaCl , and daunorubicin was biosynthesized after the existence of propionyl CoA. There was also a relationship between the enzyme activities and the daunorubicin biosynthesis in parent strain SIPI 1482. It had lower enzyme activity of MDC in GM medium, but its enzyme activity of MDC increased by the addition of 2% NaCl. The investigation indicated that the precursor of daunorubicin, propionyl CoA was formed through pathway of MCT in SIPI 1482, and MDC pathway was induced by 2% NaCl. So the daunorubicin production increased depending on the regulatory of Na +. MDC was soluble and located in the membrane of cells.