Cosynthesis of monofluoroacetate and 4-fluorothreonine by resting cells of blocked mutants of Streptomyces cattleya NRRL8057

Abstract

Streptomyces cattleya NRRL 8057 produces monofluoroacetate and 4-fluorothreonine from inorganic fluoride. Mutants blocked in fluorometabolite production were prepared by chemical mutagenesis, and cosynthesis experiments with these blocked mutants were carried out by suspending cells of one blocked mutant in the supernatant broth of another blocked mutant. The harvest age of the cells, pH of the buffer, potassium fluoride concentration and glycerol supplementation were optimized for the monofluoroacetate production by a resting-cell suspension of S. cattleya. Successful cosynthesis with pairs of the mutants characterized four distinctive blocked sites in the order N-82, N-44, N-43 and N-47. Additional preparation of blocked mutants by UV irradiation and their cosynthesis assay confirmed that U-303, U-304, U-400 and U-500 were blocked in later steps than N-47. O’Hagan et al. recently proposed that fluoroacetaldehyde, the hypothetical precursor of monofluoroacetate and 4-fluorothreonine, derives from 5′-fluoro-5′-deoxyadenosine, the first fluorinated metabolite synthesized from S-adenosyl- l-methionine and inorganic fluoride by the novel enzyme ‘fluorinase’. We were able to detect fluorinase activity in crude extracts of wild type and N-47 mutant strains, but not in the other mutant strains whose blocked steps flanked that of N-47.