A Thiamine-Dependent Enzyme Utilizes an Active Tetrahedral Intermediate in Vitamin K Biosynthesis

详细信息    查看全文

• 作者：Haigang Song ; Chen Dong ; Mingming Qin ; Yaozong Chen ; Yueru Sun ; Jingjing Liu ; Wan Chan ; Zhihong Guo
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：June 15, 2016
• 年：2016
• 卷：138
• 期：23
• 页码：7244-7247
• 全文大小：321K
• 年卷期：0
• ISSN：1520-5126

文摘

Enamine is a well-known reactive intermediate mediating essential thiamine-dependent catalysis in central metabolic pathways. However, this intermediate is not found in the thiamine-dependent catalysis of the vitamin K biosynthetic enzyme MenD. Instead, an active tetrahedral post-decarboxylation intermediate is stably formed in the enzyme and was structurally determined at 1.34 Å resolution in crystal. This intermediate takes a unique conformation that allows only one proton between its tetrahedral reaction center and the exo-ring nitrogen atom of the aminopyrimidine moiety in the cofactor with a short distance of 3.0 Å. It is readily convertible to the final product of the enzymic reaction with a solvent-exchangeable proton at its reaction center. These results show that the thiamine-dependent enzyme utilizes a tetrahedral intermediate in a mechanism distinct from the enamine catalytic chemistry.