Studies of Microbial Mechanism for Fluoride Incorporation into Organic Compounds

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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.