NADPH-dependent formation of thymidine diphosphodihydrostreptose from thymidine diphospho-D-glucose in a cell-free system from Streptomyces griseus and its correlation with streptomycin biosynthesis.

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When thymidine diphospho‐d‐[U‐14C]glucose was incubated with a cell‐free extract from a streptomycin‐producing strain of Streptomyces griseus in the presence of NADPH, Radioactive dTDP‐Dihydrosteptose Was formed in addition to radioactive dTDP‐4‐keto‐6‐deoxyglucose and dTDP‐rhamnose. Dihydrostreptose was identified by chromatographic, gas chromatographic and electrophoretic comparison with synthetic dihydrostreptose characterized by its nuclear magnetic resonance spectrum. dTDP‐dihydrostreptose is very labile and decomposes to dihydrostreptose monophosphate and further to free dihydrostreptose. dTDP‐dihydrostreptose and dTDP‐rhamnose were also obtained when dTDP‐4‐keto 6‐deoxyglucose was the substrate of the reaction. Dihydrostreptose synthesis could be inhibited completely by 1 mM p‐chloromercuribenzoate, whereas rhamnose formation was not inhibited. In the course of fermentation the activities of arginine: x‐amidinotransferase, an enzyme involved in streptomycin biosynthesis, and of the enzymatic activity for dTDP‐dihydrostreptose formation ran parallel and reached a maximum before onset of streptomycin formation. A good correlation between the activity of “dTDP‐dihydrostreptose synthase”, arginine : x‐amidinotransferase activity and streptomycin production was found in several strains of S. griseus. No dihydrostreptose formation could be detected in a hydroxystreptomycin‐producing strain of S. griseocarneus. Streptomycin but not dihydrostreptomycin could be detected in the fermentation medium of the S. griseus strain used for preparation of the cell‐free extract. The role of dTDP‐dihydrostreptose in streptomycin biosynthesis is at present unknown.