5ej9
EcMenD-ThDP-Mn2+ complex soaked with 2-ketoglutarate for 2 min and isochorismate for 13 min
Structural highlights
FunctionMEND_ECOLI Catalyzes the thiamine diphosphate-dependent decarboxylation of 2-oxoglutarate and the subsequent addition of the resulting succinic semialdehyde-thiamine pyrophosphate anion to isochorismate to yield 2-succinyl-5-enolpyruvyl-6-hydroxy-3-cyclohexene-1-carboxylate (SEPHCHC).[1] [2] Publication Abstract from PubMedEnamine is a well-known reactive intermediate mediating essential thiamine-dependent catalysis in central metabolic pathways. How-ever, this intermediate is not found in the thiamine-dependent catal-ysis of the vitamin K biosynthetic enzyme MenD. Instead, an active tetrahedral post-decarboxylation intermediate is stably formed in the enzyme and structurally determined at 1.34 A resolution in crystal. This intermediate takes a unique conformation that allows only one proton between its tetrahedral reaction center and the exo-ring ni-trogen atom of the aminopyrimidine moiety in the cofactor with a short distance of 3.0 A. 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. A thiamine-dependent enzyme utilizes an active tetrahedral intermediate in vitamin K biosynthesis.,Song H, Dong C, Qin M, Chen Y, Sun Y, Liu J, Chan W, Guo Z J Am Chem Soc. 2016 May 23. PMID:27213829[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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