On the mechanism of the reaction catalyzed by glucose 6-phosphate dehydrogenase.
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Cosgrove MS, Naylor C, Paludan S, Adams MJ, Levy HR
On the mechanism of the reaction catalyzed by glucose 6-phosphate dehydrogenase.
Biochemistry. 1998 Mar 3;37(9):2759-67.
- PubMed ID
- 9485426 [ View in PubMed]
- Abstract
The catalytic mechanism of glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides was investigated by replacing three amino acids, His-240, Asp-177, and His 178, with asparagine, using site-directed mutagenesis. Each of the mutant enzymes was purified to homogeneity and characterized by substrate binding studies and steady-state kinetic analyses. The three-dimensional structure of the H240N glucose 6-phosphate dehydrogenase was determined at 2.5 A resolution. The results support a mechanism in which His-240 acts as the general base that abstracts the proton from the C1-hydroxyl group of glucose 6-phosphate, and the carboxylate group of Asp-177 stabilizes the positive charge that forms on His-240 in the transition state. The results also confirm the postulated role of His-178 in binding the phosphate moiety of glucose 6-phosphate.