Nachweis eines enzymgebundenen Zwischenprodukts bei der Umwandlung von Thymidindiphosphat‐D‐glucose in Thymidindiphosphat‐L‐rhamnose in E. coli B

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Abstract
An incubation mixture of TDP‐D‐glucose and a purified enzyme extract from E. coli B containing TDP‐D‐glucose 4,6‐hydro‐lyase was treated with NaB3H4. Hydrolysis of the separated sugar nucleotide fraction yielded D‐galactose‐4‐3H but no 3H‐labelled D‐glucose. This indicates the presence of TDP‐4‐keto‐D‐glucose as an intermediate in the enzymatic conversion of TDP‐D‐glucose to TDP‐L‐rhamnose. The stereospecifity of the NaB3H4 reduction can only be explained if TDP‐4‐keto‐D‐glucose exists as an enzyme bound complex.