Summary: TDP--glucose 4,6-dehydratase, which converts TDP--glucose to TDP--4-keto-6-deoxyglucose, was purified to near-homogeneity from the daunorubicin and baumycin-producing organism sp. C5 (968-fold purification with a 41% recovery), and from the daunorubicin producer ATCC 29050 (1000-fold purification with a 37% recovery). The TDP--glucose 4,6-dehydratases from sp. C5 and were determined by SDS-PAGE and HPLC gel filtration to be homodimers with subunit relative molecular masses of 39000 and 36000, respectively. For the enzymes from both organisms, negligible activity was observed in the absence of added NAD, or when ADP-glucose, ADP-mannose, GDP-mannose, UDP-glucose or UDP-galactose was substituted for TDP--glucose as substrate. For the enzyme from sp. C5, the ' values for NAD and TDP--glucose were 19·2 μ and 31·3 μ, respectively. The ' for TDP--glucose was 309 nmol min (mg protein). For the enzyme, the ' values for NAD and TDP--glucose were 20·1 μ 34·7 μ, respectively. values were 180 nmol min (mg protein) for NAD and 201 nmol min (mg protein) for TDP--glucose. TDP was a good inhibitor of TDP--glucose 4,6-dehydratase from both organisms. The N-terminal amino acid sequence of the TDP--glucose 4,6-dehydratase from and from the erythromycin producer, , were similar, whereas the enzyme from sp. C5 contained a different N-terminal amino acid sequence from either of the other two enzymes.


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