Department of Life Science & Institute of Bioinformatics and Structural Biology, National Tsing Hua University^* Institute of BioMedical Science, National Chiao Tung University, Taiwan^** Institute of Molecular Biology, Academia Sinica, Taiwan^***
○Yi-Wei Chang^* Chih-Chien Wu^** Yuh-Ju Sun^* Hsien-Tai Chiu^** Chwan-Deng Hsiao^***

Daunorubicin (DNR) and its C-14-hydroxylated derivative doxorubicin (DXR) which produced by Streptomyces peucetius are clinically important anti-tumor agents in the treatment of a number of malignancies including leukemia, non-Hodgkin lymphoma, and breast cancer. Like many microbial secondary metabolites, DNR and DXR require a deoxyhexose component for their biological activity. The biologically important deoxy-sugar in this case is the 2,3,6-trideoxy-3-aminohexose daunosamine. According to the well characterized biosynthetic pathway of these two anti-tumor components, the last step of daunosamine biosynthesis is performed by the thymidine diphospho-4-keto-2,3,6-trideoxy-3-aminohexose reductase (DnmV). Here, two complex crystal structures of DnmV were determined. One is a binary complex structure in which DnmV coupled with cofactor NADP, and another is a ternary complex structure in which DnmV coupled with cofactor NADP and inhibitor thimidine diphosphate. These two complex structures provide insights into the conformation of DnmV and help us to elucidate the detail inhibition mechanism of TDP. Furthermore, modeling of the saccharide moieties of the substrate in the active site based on the DnmV/NADP/TDP ternary complex structure allows us to propose a detailed catalytic mechanism for DnmV. These studies should lead to facilitate efforts to engineer strains that produce larger quantities of more capable and more valuable microbial metabolites.