Biosynthesis of streptothricin F. Part 6. Formation and intermediacy of D-glucosamine in Streptomyces L-1689-23

Abstract

Aspects of the biosynthesis of the D-gulosamine moiety of the antibiotic streptothricin F have been studied with stable isotopes. After having obtained substantial incorporation (ca. 9%) of [1-¹⁴C]-D-glucosamine into the total compound, [2-¹³C, ¹⁵N]-D-glucosamine was synthesized and fed to Streptomyces L-1689-23. Analysis of the ¹³C n.m.r. spectrum of the derived antibiotic reveals a doublet (J_CN 11.4 Hz) for the C-8 resonance (3.1% enrichment in both ¹³C and ¹⁵N), indicating the intact incorporation of the material fed and establishing D-glucosamine as a direct precursor to streptothricin. [1-²H]-D-Glucose has been synthesized and incorporated into streptothricin with retention of the deuterium label at 7-H (1.8% enrichment) and incorporation of deuterium at 17-H/18-H (0.4% enrichment); data from the incorporation of [1-¹⁴C]-D-glucose that had been co-fed indicate extensive metabolism into other parts of the structure. Incorporation of [2-²H]-D-glucose leads only to deuterium enrichment at 17-H/18-H (0.09% enrichment), indicating that 2-H is apparently lost in the phosphoglucose isomerase reaction of this organism.