CLONING OF THE GENES ENCODING THYMIDINE DIPHOSPHOGLUCOSE 4,6-DEHYDRATASE AND THYMIDINE DIPHOSPHO-4-KETO-6-DEOXYGLUCOSE 3,5-EPIMERASE FROM THE ERYTHROMYCIN-PRODUCING SACCHAROPOLYSPORA-ERYTHRAEA

Genes involved in deoxysugar metabolism, encoding thymidine diphospho (TDP)-glucose 4,6-dehydratase (gdh) and a putative TDP-4-keto-6-deoxyg lucose 3,5-epimerase (kde), were cloned from the erythromycin (Er)-pro ducing Saccharopolyspora erythraea by means of an oligodeoxynucleotide corresponding to a segment of the purified Gdh protein. Determination of the nucleotide sequence established that kde lies 3' to gdh. The f unction of gdh was confirmed by an enzymatic assay following expressio n of the gene in Escherichia coli. Southern analysis indicated that Sa . erythraea contains only one copy of gdh and kde. It was not possible to establish whether these genes are required for Er biosynthesis, bu t they appear to be essential for cellular metabolism, since resolutio n of a partial diploid containing a wt and a disrupted copy of gdh alw ays maintained the wt gene. These loci do not lie within or near the k nown boundaries of the cluster of Er-production and -resistance genes, nor do they appear to be flanked by other deoxysugar biosynthesis gen es.