Bildung eines oxoäthylverzweigten Zuckers aus Thymidindiphosphatglucose und Pyruvat mit einem zellfreien. System aus Streptomyces aureofaciens / Formation of an Oxoethyl-branched Sugar from Thymidine Diphospho-ᴅ-glucose and Pyruvate with a Cell Free System from Streptomyces aureofaciens

Incubation of thymidine diphospho(TDP)-ᴅ-[U- 14 C] -glucose with a cell-free extract from Streptomyces aureofaciens and subsequent hydrolysis of the nucleotide sugars led to the formation of 4 radioactive products (I -IV ). Addition of pyruvate to the incubation caused an increase in the amount of I I I and a decrease in that of II. Product I was identified as 4-keto-6-deoxyglucose. Product III was isolated on a preparative scale as the methylglycoside and was identified as α-methyl- 2,6-dideoxy-4-C-[1'-oxoethyl]-ʟ-lyxo-hexopyranoside (Fig. 1, 3) from its NM R spectrum and by its borate complex formation, which established the cis configuration of the hydroxyl groups at C-3 and C-4. The oxoethyl-branched sugar formed in the cell-free system is epimer at C-3 with the sugar formed in vivo by S. aureofaciens. The reason for this difference is not clear. Product II could be tentatively formulated as 4-keto-2,6-dideoxy-ʟ-lyxo-hexopyranose (6 ) on the basis of its chromatographic and chemical properties and its reduction by sodiumborohydride to two sugars. The products II - IV were also obtained when TDP-4-keto-6-deoxyglucose was the substrate of the reaction. Addition of thiaminepyrophosphate to the incubation in the presence of pyruvate did not increase the yield of III . The increasf in the amount of III formed in the presence of pyruvate could be inhibited by addition of glyoxylic acid. After incubation of [α- 14 C]-hydroxethyl-thiaminepyrophosphate with TDP-glucose in the cell-free extract no radioactive III could be detected.