Studies of Microbial Mechanism for Fluoride Incorporation into Organic Compounds

通过优化培养条件和对产生菌进行诱变，提高了卡特兰链霉菌产氟乙酸的能力。筛选出K培养基（可溶性淀粉2.5%，豆粕1.5%，酵母抽提物0.2%，氟化钾0.058%）为最佳培养基。以出发菌株NRRL 8057为出发菌株，经亚硝基胍处理，获得了一株改良菌株NTG-29。另一株菌株NTG-29-PRO-34是从卡氏链霉菌NTG-29出发，经原生质体再生获得的。在菌株的改良过程中，产氟乙酸能力与产孢能力呈一定的相关性。^<14>C-掺入研究表明，氟乙酸的前体是丙酮酸之前的D-葡萄糖同化途径中的代谢产物。这是基于以下结果。在所测试的标记化合物中，D-14 <14>C-葡萄糖的放射性最有效地被转化为氟乙酸盐。13 <14>C-掺入草酸盐、L-苹果酸盐和2-酮戊二酸盐揭示，<14>13 <14>C-葡萄糖的13 C在掺入氟乙酸盐之前遵循不包括丙酮酸盐、琥珀酸盐和L-天冬氨酸盐的途径。羟基丙酮酸通过细胞提取物转化为氟乙酸需要辅酶A、焦磷酸硫胺素、氯化锰，而丙酮酸不需要它们。羟基丙酮酸的转化可以解释如下。它被活化为O-磷酸乙二醇酰CoA，然后在C-2位被氟阴离子进行亲核取代反应，然后水解释放氟乙酸酯。

The fluoroacetate production by Streptomyces cattleya was enhanced by optimization of cultivation conditions and mutation of the producer strain. Medium K(solable starch 2.5%, soybean meal 1.5%, yeast extyract 0.2%, potassium fluoride 0.058%)was selected as the best culture medium. An improved strain Str. cattleya NTG-29 was derived from the original strain, NRRL 8057, by nitrosoguanidine treatinerit. Another strain, NTG-29-PRO-34, was derived from Str. cattlya NTG-29 through the protoplast, regeneration. In the course of improving strain, the ability of producing fluoroactate and sporulation appeared to be associted with each other. ^<14>C-Incorporation studies suggested that the precursor of fluoroacetate is a metabolite in the D-glucose assimilation pathway before pyruvate. This is based on the following flndings. Among the labeled compounds tested, radioactivity of D- ^<14>C-glucose was most efficiently inecorporated to fluoroacetate. ^<14>C-Incorporation into oxalate, L-malate and 2-oxoglutarate revealed that ^<14>C of ^<14>C-glucose followed a route which does not include pyruvate, suceingte and L-aspartate before it was incorporated to fluoroacetate. The conversion of' hydroxypyruvate to fluoroacetate by cell extract required coenzyme A, thiamine pyrophosphate, manganese chloride, while that of pyruvate did not require them. The conversion of hydroxypyruvate can be explained as follows. It is activated to O-phosphoglycolylCoA, then undergoes nucleophilic substitution reaction by fluoride anion at C-2 position followed by hydrolysis to release fluoroacetate.