Biosynthesis of streptomycin. dTDP-dihydrostreptose synthase from Streptomyces griseus and dTDP-4-keto-L-rhamnose 3,5-epimerase from S. griseus and Escherichia coli Y10

Biochim Biophys Acta. 1979 May 10;568(1):243-52. doi: 10.1016/0005-2744(79)90291-2.


dTDP-dihydrostreptose synthase from Streptomyces griseus was purfied about 50-fold by removal of protein with polyethyleneimine, (NH4)2SO4 fractionation and gel filtration on Ultrogel AcA44. The synthase preparation was free of dTDP-4-keto-L-rhamnose 3,5-epimerase (dTDP-4-keto-6-deoxy-D-glucose 3,5-epimerase, EC activity. A new enzyme assay using Escherichia coli Y10 as source for the epimerase and dTDP-glucose 4,6-dehydratase (dTDP-glucose 4,6-hydro-lyase, EC was developed. In the presence of excess epimerase the apparent Km for dTDP-4-keto-6-deoxy-D-glucose was determined to be 25 microM. The molecular weight of epimerase and synthase were determined by their elution volumes from a Sephadex G-100 column to be approx. 67,000 and 32,000, respectively. The pH optimum for the epimerase was between 7.5 and 8.5. The intermediate formation of dTDP-4-keto-L-rhamnose in the epimerase reaction could be shown by detection of 6-deoxy-[3H]talose after NaB3H4 reduction. Results which indicate the existence of dTDP-4-keto-6-rhamnose as a free intermediate in the epimerase reaction are reported.

MeSH terms

  • Carbohydrate Epimerases / isolation & purification
  • Carbohydrate Epimerases / metabolism*
  • Escherichia coli / enzymology*
  • Kinetics
  • Nucleoside Diphosphate Sugars
  • Rhamnose / analogs & derivatives
  • Streptomyces griseus / enzymology*
  • Streptomycin / biosynthesis*
  • Sugar Alcohol Dehydrogenases


  • Nucleoside Diphosphate Sugars
  • Sugar Alcohol Dehydrogenases
  • dTDP-dihydrostreptose synthase
  • Carbohydrate Epimerases
  • Rhamnose
  • Streptomycin